Compositions and methods for making porous structures with high surface area

Abstract

A porous structure includes from 5 wt.% to 95 wt.% hollow glass bodies and from 5 wt.% to 95 wt.% of a secondary phase based on the total weight of the porous structure. The hollow glass bodies include a silica-containing glass. The hollow glass bodies and the secondary phase are sintered together and at least a portion of the hollow glass bodies are breached. Voids defined within the individual breached hollow glass bodies open into one another to form cavities that extend through the porous structure and to outer surfaces thereof. The porous structure has greater than or equal to 50% porosity by volume and may have a specific surface area greater than or equal to 5 m2 / g. The porous structures can be incorporated into CO2 capture processes.

Description

COMPOSITIONS AND METHODS FOR MAKING POROUS STRUCTURES WITH HIGH SURFACE AREACROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Chinese Application Serial No. 202310892569.2 filed on July 20, 2023, the content of which is relied upon and incorporated herein by reference in their entirety.BACKGROUNDField

[0002] The present disclosure generally relates to porous structures, more specifically, to honeycomb-shaped porous structures for use as substrates for carbon dioxide capture systems and processes.Technical Background

[0003] The amount of carbon dioxide (CO2) in the Earth's atmosphere has steadily increased since the Industrial Revolution due to fossil fuel combustion technologies like coal- fired power plants and gasoline / diesel based automobiles. Such CO2 increase has raised global warming concerns and prompted the global community to work towards controlling CO2 emissions and / or capturing CO2 from the atmosphere to reduce build-up of CO2 in the environment. One solution for CO2 capture is to use solid adsorbents to capture CO2 directly from the air or from point sources such as power plants. Ceramic porous substrates, such as porous ceramic honeycombs are considered to be a potential carrier for adsorbents for CO2 capture applications.SUMMARY

[0004] According to a first aspect disclosed herein, a porous structure may comprise from 5 wt.% to 95 wt.% hollow glass bodies based on the total weight of the porous structure and from 5 wt.% to 95 wt.% of a secondary phase based on the total weight of the porous structure. The hollow glass bodies may comprise a silica-containing glass. The hollow glass bodies and the secondary phase are sintered together and at least a portion of the hollow glass bodies are breached. Voids defined within the individual breached hollow glass bodies open into one another to form cavities that extend through the porous structure and to outer surfaces thereof.The porous structure may have greater than or equal to 50% porosity by volume and may have a specific surface area greater than or equal to 5 m2 / g.

[0005] A second aspect disclosed herein may include the first aspect, wherein the specific surface area of the porous structure may be greater than or equal to 10 m2 / g, or even greater than or equal to 20 m2 / g.

[0006] A third aspect disclosed herein may include either one of the first or second aspects, wherein the porosity of the porous structure may be greater than or equal to 55%, or even greater than or equal to 60%.

[0007] A fourth aspect disclosed herein may include any one of the first through third aspects, wherein the secondary phase may comprise nano-sized inorganic particles having a specific surface area of greater than or equal to 10 m2 / g; nano-sized crystal grains comprising reaction products of a reaction between the silica-containing glass and a coarse inorganic particle having specific surface area less than 10 m2 / g and containing oxides, hydroxides, salts, or combinations thereof of alkali metals or alkaline earth metals; or combinations thereof.

[0008] A fifth aspect disclosed herein may include the fourth aspect, wherein the secondary phase may comprise the nano-sized inorganic particles having high specific surface area of greater than or equal to 10 m2 / g.

[0009] A sixth aspect disclosed herein may include the fifth aspect, wherein the nano-sized inorganic particles may have a specific surface area of greater than or equal to 20 m2 / g, greater than or equal to 50 m2 / g. or even greater than or equal to 100 m2 / g.

[0010] A seventh aspect disclosed herein may include either one of the fifth or sixth aspects, wherein the nano-sized inorganic particles may have a median particle size (d50) of from 0. 1 nanometers to 100 nanometers.

[0011] An eighth aspect disclosed herein may include any one of the fifth through seventh aspects, wherein the nano-sized inorganic particles may comprise gamma alumina, zirconia, zeolite, magnesium oxide, silica, CeCh, TiCh, or combinations of these.

[0012] A ninth aspect disclosed herein may include any one of the fifth through eighth aspects, wherein the nano-sized inorganic particles may comprise gamma alumina.

[0013] A tenth aspect disclosed herein may include any one of the fourth through ninth aspects, wherein the secondary' phase may comprise the nano-sized crystal grains comprising0the reaction product of the reaction between the silica-containing glass and the coarse inorganic particles.

[0014] An eleventh aspect disclosed herein may include the tenth aspect, wherein the coarse inorganic particles may have a specific surface area of less than 10 m2 / g.

[0015] A twelfth aspect disclosed herein may include either one of the tenth or eleventh aspects, wherein the coarse inorganic particles may have an average particle size of from about 100 nanometers to about 100 micrometers.

[0016] A thirteenth aspect disclosed herein may include any one of the tenth through twelfth aspects, wherein the coarse inorganic particles may comprise MgO, Mg(OH 2, CaO, Ca(OH)2, Ca3(PO4)2, CaCO3, Li2O, LI2CO3, Li2BO3, Na2O, NaOH, Na2CO3, K2O, KOH, K2CO3, or any combinations thereof.

[0017] A fourteenth aspect disclosed herein may include any one of the tenth through thirteenth aspects, wherein the coarse inorganic particles may comprise MgO.

[0018] A fifteenth aspect disclosed herein may include any one of the tenth through fourteenth aspects, wherein the secondary phase may comprise at least one magnesium-based crystal phase selected from forsterite, clinoenstatite, diopside, or combinations thereof; at least one calcium-based crystal phase selected from wollastonite, pseudo wollastonite, kilchoanite, crostobalite; or combinations thereof.

[0019] A sixteenth aspect disclosed herein may include the fourth aspect, wherein the secondary7phase may comprise nanosized inorganic particles having a specific surface area of greater than or equal to 10 m2 / g and nano-sized crystal grains comprising reaction products of a reaction between the silica-containing glass and the coarse inorganic particles having specific surface area less than 10 m2 / g and containing oxides, hydroxides, salts, or combinations thereof of alkali metals or alkaline earth metals.

[0020] A seventeenth aspect disclosed herein may include the sixteenth aspect, wherein the porous structure may comprise one or more cry stalline phases selected from roedderite, corundum, zirconia, or combinations of these.

[0021] An eighteenth aspect disclosed herein may include any one of the first through seventeenth aspects, wherein the porous structure may comprise a glass phase.

[0022] A nineteenth aspect disclosed herein may include any one of the first through eighteenth aspects, wherein the plurality of hollow glass bodies may comprise borosilicateglass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate glass, or combinations thereof.

[0023] A twentieth aspect disclosed herein may include any one of the first through nineteenth aspects, wherein the porous structure may have a D-factor of greater than or equal to 0.5, wherein the D-factor is equal to (d5o-dio) / dso, dso refers to a mean pore diameter of the porous structure at which 50% by volume of the open porosity of the porous structure has been intruded by mercury during a porosimetry measurement, and dio is equal to the pore diameter at which 90% by volume of the open porosity7of the porous structure has been intruded by mercury during a porosimetry measurement.

[0024] A twenty-first aspect disclosed herein may include any one of the first through twentieth aspects, wherein the porous structure may have a median pore size of from 1 pm to 50 pm, or from 2 pm to 20 pm.

[0025] A twenty-second aspect disclosed herein may include any one of the first through twenty -first aspects, wherein the porous structure may have a honeycomb shape comprising a plurality of elongate channels extending through at least a portion of the porous structure, wherein the porous structure may have a cell density7of less than 400 cells per inch and a web thickness between cells of from 2 mils to 8 mils, where the cell density refers to a number of elongate channels per square inch of cross-section of the porous structure.

[0026] A twenty-third aspect disclosed herein may include any one of the first through twenty-second aspects, wherein the porous structure may comprise a size and shape that is within 15% of a size and shape of an extruded green structure prior to firing to convert the extruded green structure into the porous structure.

[0027] A twenty -fourth aspect disclosed herein may include any one of the first through twenty-third aspects, further comprising one or more CO2 adsorbents deposited within the cavities of the porous structure.

[0028] A twenty-fifth aspect disclosed herein may include the twenty-fourth aspect, wherein the CO2 adsorbents may comprise PEI, MEA, DEA, PPI, PPA, NaOH, Na2COs, NaHCCh, KOH, K2CO3, KHCO3, or combinations thereof.

[0029] A twenty-sixth aspect disclosed herein may include either one of the twenty -fourth or twenty -fifth aspects, wherein the CO2 adsorbents may be bonded to surfaces of the porous structure defining the cavities.

[0030] A twenty -seventh aspect disclosed herein may include any one of the twenty-fourth through twenty -sixth aspects, wherein the porous structure does not have an interlayer disposed between surfaces of the porous structure and the CO2 adsorbents bonded thereto.

[0031] A twent -eighth aspect disclosed herein may include any one of the twenty -fourth through twenty-eighth aspects, comprising a CO2 capture process comprising the porous structure of any one of the twenty-fourth through twenty-eighth aspects, wherein the CO2 capture process may' further comprise an adsorption-desorption unit and the porous structure may be integrated into the adsorption-desorption unit.

[0032] A twenty -ninth aspect disclosed herein may be directed to a composition for making a ceramic honey comb. The composition may comprise a plurality of hollow glass bodies comprising a silica-containing glass, a secondary phase precursor, a liquid vehicle, and an organic system. The secondary phase precursor may comprise nanosized inorganic particles having a specific surface area of greater than or equal to 10 m2 / g; coarse inorganic particles having specific surface area less than 10 m2 / g and comprising oxides, hydroxides, salts, or combinations thereof of alkali metals or alkaline earth metals; or combinations thereof.

[0033] A thirtieth aspect disclosed herein may include the twenty -ninth aspect, comprising from 50 vol.% to 95 vol.% of the hollow glass bodies and from 5 vol.% to 50 vol.% of the secondary phase precursor, wherein the volume percentages are based on the total bulk volume of inorganic solid components of the composition.

[0034] A thirty-first aspect disclosed herein may include either one of the twenty -ninth or thirtieth aspects, wherein the silica-containing glass may comprise borosilicate glass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate glass, or combinations of these.

[0035] A thirty -second aspect disclosed herein may include any one of the tw enty-ninth through thirty-first aspects, wherein the secondary phase precursor may comprise the nanosized inorganic particles.

[0036] A thirty-third aspect disclosed herein may include the thirty-second aspect, wherein the nanosized inorganic particles may have a specific surface area of greater than or equal to 10 m2 / g.

[0037] A thirty-fourth aspect disclosed herein may include either one of the thirty -second or thirty-third aspects, wherein the nanosized inorganic particles may comprise gammaalumina, zirconia, zeolite, magnesium oxide, silica, CeCh. TiCh, or combinations thereof.

[0038] A thirty-fifth aspect disclosed herein may include any one of the twenty-ninth through thirty-first aspects, wherein the secondary phase precursor may comprise the coarse inorganic particles comprising the oxides, hydroxides, salts, or combinations thereof of the alkali metals or alkaline earth metals.

[0039] A thirty-sixth aspect disclosed herein may include the thirty-fifth aspect, wherein the coarse inorganic particles may comprise MgO, Mg(0H)2, CaO, Ca(OH)2, Ca?(PO4)2, CaCO3, Li2O, L12CO3, Li3BO3, Na2O, NaOH, Na2CO3, K2O, KOH, K2CO3, or combinations thereof.

[0040] A thirt -seventh aspect disclosed herein may include any one of the twenty-ninth through thirty-sixth aspects, wherein the organic system may comprise one or more of methocel, CMC, lubricants, PVP, PVA, or combinations thereof.

[0041] A thirty -eighth aspect disclosed herein may include any one of the twenty-ninth through thirty-seventh aspects, wherein the liquid vehicle may be water, one or more alcohols, or combinations thereof.

[0042] A thirty-ninth aspect disclosed herein may include any one of the twenty-ninth through thirty-eighth aspects, comprising a porous structure prepared from the composition of any one of the twenty-ninth through thirty -eighth aspects.

[0043] A fortieth aspect disclosed herein may include any of the twenty -ninth through thirty eighth aspects, and may be directed to a porous structure prepared by a process that may comprise preparing the composition of any one of the twenty-ninth through thirty-eighth aspects; forming a green structure from the composition; and firing the green structure at a temperature less than or equal to 1000 °C, or even less than or equal to 900 °C. The porous structure may have a porosity7of greater than or equal to 50%, and a specific surface area of greater than or equal to 5 m2 / g.

[0044] A forty-first aspect disclosed herein may include the fortieth aspect, wherein the porous structure may have a size and shape that is within 15%, or even within 1% of a size and shape of the green structure before firing.

[0045] A forty-second aspect disclosed herein may include either one of the fortieth or forty-first aspects, wherein the secondary phase precursor may comprise the nano-sized inorganic particles, and firing the green structure may bond the hollow glass microspheres and the nano-sized inorganic particles together and may breach at least a portion of the hollow glassbodies to form the porous structure having the porosity greater than or equal to 50% and the specific surface area of greater than or equal to 5 m2 / g.

[0046] A forty-third aspect disclosed herein may include any one of the fortieth through forty-second aspects, wherein the secondary phase precursor may comprise the coarse inorganic particles comprising the oxides, hydroxides, salts, or combinations thereof of the alkali metals or alkaline earth metals, and firing the green structure may cause a reaction between the silica-containing glass of the hollow glass bodies to produce nano-sized crystal grains and may breach at least a portion of the hollow glass bodies to form the porous structure having a porosity of greater than or 50% and the specific surface area of greater than or equal to 5 m2 / g.

[0047] A forty-fourth aspect disclosed herein may include any one of the fortieth through forty -third aspects, wherein firing the green structure may comprise ramping the green structure to the peak firing temperature of less than or equal to 1000 °C and holding the green structure at the peak firing temperature for a period of from 1 hour to 10 hours.

[0048] A forty-fifth aspect disclosed herein may include any one of the fortieth through forty-fourth aspects, wherein the porous structure further may comprise a CO2 adsorbent bonded to surfaces of cavities of the porous structure, and the process further may comprise bonding the CO2 adsorbent to the porous structure.

[0049] A forty-sixth aspect disclosed herein may include any one of the fortieth through forty-fifth aspects, wherein bonding the adsorbent to the porous structure does not include applying an interlayer between the surfaces of the porous structure and the CO2 adsorbent.

[0050] Additional features and advantages of the subject matter described and claimed herein will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description, which follows, the claims, as well as the appended drawings.

[0051] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. Thedrawings illustrate the various embodiments described herein, and together with the description sen e to explain the principles and operations of the claimed subj ect matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 schematically depicts a front perspective view of a porous structure, according to one or more embodiments shown and described herein;

[0053] FIG. 2 schematically depicts a perspective view of another porous structure, according to one or more embodiments shown and described herein;

[0054] FIG. 3 schematically depicts a cross-sectional view of a carbon capture device comprising a porous structure having a carbon dioxide adsorbent, according to one or more embodiments show n and described herein;

[0055] FIG. 4 schematically depicts one embodiment of a carbon dioxide capture system comprising porous structures of the present disclosure, according to one or more embodiments shown and described herein;

[0056] FIGS. 5A, 5B, 5C, 5D, and 5E are scanning electron microscope (SEM) images showing a surface morphology of porous structures made from hollow glass microspheres and gamma alumina (y-AhOs) particles and fired at different firing temperatures, according to one or more embodiments shown and described herein;

[0057] FIG. 6 graphically depicts X-Ray Diffraction (XRD) plots for the porous structures of FIGS. 5A-5E, according to one or more embodiments shown and described herein;

[0058] FIG. 7 graphically depicts pore size distributions for the porous structures of FIGS. 5A-5E, according to one or more embodiments shown and described herein;

[0059] FIGS. 8 A, 8B, 8C, and 8D are SEM images showing a surface morphology of porous structures made from hollow glass microspheres and magnesium oxide (MgO) particles and fired at different firing temperatures, according to one or more embodiments shown and described herein;

[0060] FIGS. 9A, 9B, 9C, and 9D are SEM images of the porous structures of FIGS. 8A, 8B. 8C, and 8D, respectively, taken a higher resolution, according to one or more embodiments shown and described herein;

[0061] FIG. 10 graphically depicts XRD plots for porous structures prepared from a composition comprising hollow glass microspheres and MgO particles and fired at different firing temperatures, according to one or more embodiments shown and described herein;

[0062] FIG. 11 graphically depicts pore size distributions for the porous structures of FIGS. 8A, 8B, 8C, and 8D, according to one or more embodiments shown and described herein;

[0063] FIGS. 12A, 12B, 12C, and 12D are SEM images showing a surface morphology of porous structures made from a composition comprising hollow glass microspheres, 20 vol.% MgO particles, and 15 vol.% gamma alumina particles and fired at different firing temperatures, according to one or more embodiments shown and described herein;

[0064] FIGS. 13A, 13B, 13C, and 13D are SEM images of the porous structures of FIGS. 12A, 12B, 12C, and 12D, respectively, taken a higher resolution, according to one or more embodiments shown and described herein;

[0065] FIGS. 14A, 14B, 14C, and 14D are SEM images showing a surface morphology' of porous structures made from a composition comprising hollow glass microspheres, 10 vol.% MgO particles, and 10 vol.% gamma alumina particles and fired at different firing temperatures, according to one or more embodiments shown and described herein;

[0066] FIGS. 15A, 15B, 15C, and 15D are SEM images of the porous structures of FIGS. 14A, 14B, 14C, and 14D, respectively, taken a higher resolution, according to one or more embodiments show n and described herein;

[0067] FIG. 16 graphically depicts pore size distributions for the porous structures of FIGS. 12A, 12B, 12C, and 12D, according to one or more embodiments shown and described herein; and

[0068] FIG. 17 graphically depicts pore size distributions for the porous structures of FIGS. 14A. 14B, 14C, and 14D, according to one or more embodiments shown and described herein.DETAILED DESCRIPTION

[0069] Reference will now be made in detail to various embodiments of the porous structures, batch compositions for making the porous structures, CO2 capture devices incorporating the porous structures, and methods of the present disclosure. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The present disclosure is directed to honeycomb-shaped porous structures having highporosity and high specific surface area. The porous structures comprise from 5 wt.% to 95 wt.% hollow glass bodies based on the total weight of the porous structure, the hollow glass bodies comprising a silica-containing glass. The porous structures further comprise from 5 wt.% to 95 wt.% of a secondary phase based on the total weight of the porous structure. The hollow glass bodies and the secondary phase are sintered together, and at least a portion of the hollow glass bodies are breached. The voids defined within the individual breached hollow glass bodies open into one another to form cavities that extend through the porous structure and to outer surfaces thereof. The porous structure may have greater than or equal to 50% porosity by volume and a specific surface area greater than or equal to 5 m2 / g.

[0070] The porous structures disclosed herein have both high specific surface area of greater than or equal to 5 m2 / g, and high porosity, such as greater than or equal to 50% porosity. Additionally, the porous structures, after firing, may have a composition comprising constituents that can enhance the performance of alkaline sorbents, such as but not limited to PEI, MEA, DEA, PPI, PPA, etc., loaded onto the porous structure. One or more of the crystalline phases formed during firing of the porous structures may enhance performance of the adsorbents loaded thereon. Further, the compositions of the ceramic honeycombs disclosed herein may have low firing temperature, such as peak firing temperatures of less than about 1000 °C, less than about 950 °C, or even less than or equal to 900 °C, compared to conventional cordierite honeycombs, which are fired at temperatures greater than about 1400 °C. The porous structures may be utilized as substrates for CO2 capture applications. The high specific surface area of greater than or equal to 5 m2 / g for the porous structure may enable the carbon dioxide adsorbents to be applied directly to the surfaces of the porous structure without first applying an interlayer, among other features.

[0071] As used herein, the term "hollow bodies" refers to particles comprising a shell that is made of glass and that surrounds an internal volume containing a substance that is not glass, such as air or other gas.

[0072] As used herein, the term "green structure" refers to a structure formed of the compositions disclosed herein that has not been subjected to firing.

[0073] As used herein, the term "peak firing temperature" refers to the maximum temperature during the firing process, at which maximum temperature, the green structure is maintained for a period of time before being gradually cooled down to ambient temperature.

[0074] As used herein, the term "dwell" or "dwell period" may refer to one or more periods of time during a firing process when the temperature of the green structures are maintained relatively constant, such as maintaining the temperature of the green structures within a specified range about a target temperature.

[0075] As used herein, the term "lower crystallization temperature" of a composition, such as a glass composition, may refer to a temperature at which one or more constituents of the composition begin to undergo devitrification and / or crystallization.

[0076] As used herein, the term "upper crystallization temperature" of a composition, such as a glass composition, may refer to a temperature at which devitrification slows significantly and crystallization proceeds at an insignificant rate.

[0077] As used herein, the term "crystallization temperature zone" refers to the temperature range between the crystallization zone lower temperature and the crystallization zone lower temperature.

[0078] As used herein, the term "cell density’" refers to a number of elongate channels of a honeycomb-shaped porous structure per unit cross-sectional area of the honeycomb-shaped porous structure and is provided in units of cells per square inch. A cell refers to the transverse cross-section of a single elongate channel.

[0079] As previously discussed, CO2 capture from the atmosphere is gaining in focus due to increasing concentration so CO2 in the Earth's atmosphere. CO2 capture processes include adsorption of CO2 from the air or from point sources, such as combustion gas vents, using one or more CO2 adsorbents. These adsorbents can be applied to a substrate. Ceramic porous substrates, such as porous ceramic honeycombs, are considered potential carrier substrates for adsorbents for these CO2 capture applications. Over the past few decades, ceramic honeycombs have been developed for and integrated into engine after-treatment systems to capture fine particulates or decompose the SO2. NOx from diesel and gasoline engine exhausts. The ceramic honeycombs provide reduced pressure drop, lower energy consumption over the lifetime of the filters, ability to be regenerated, long service lifetime, reduced solid waste, and lower cost of ownership over the life cycle compared to other types of substrates. The honeycombs used for engine after-treatment are ceramic-based (e.g., cordierite, AT. SiC. etc.), and have been engineered to withstand high temperatures (e.g., 800 °C or higher) and high thermal shock. For CO2 capture from ambient air or point sources, such as flue gas, such properties are not necessary. Further, the ceramic honeycombs, which are typically constructed of cordierite,generally have low specific surface area of typically less than 1 m2 / g or even less than 0.5 m2 / g. In order to provide sufficient surface area for CO2 capture, the ceramic honeycombs with low specific surface area must first be treated to apply an interlayer to the surfaces of the ceramic honeycomb to increase the surface area. The adsorbents for CO2 capture are then applied to the interlayer. The interlayer requires additional materials and additional process steps to produce the CO2 capture devices.

[0080] An ongoing need exists for honeycomb-shaped porous structures that have properties and performance suitable for use as honeycomb-shaped substrates for CO2 capture devices and processes and that provide low cost. The present application is directed to porous structures having high porosity of greater than or equal to 50% by volume and high surface area, such as greater than or equal to 5 m2 / g. The porous structures disclosed herein comprises hollow glass bodies and a secondary' phase having a high surface area. Tiny hollow glass bodies, also called glass bubbles, microballoons, or hollow glass "microspheres," are commercially available, such as from Dennert Poraver GMBH, 3M, Zhongke Y ah Technology, Ltd, Fibre Glast Developments Corp., Potters Industries LLC, and others. The hollow glass bodies can be arranged and processed to make particularly efficient porous structures with open porosity, which may be used as honeycomb-shaped substrates for adsorption / desorption units in CO2 capture processes. Structures with open porosity may be formed from tightly packing the hollow bodies together, bonding the hollow bodies to one another, and also breaching the hollow bodies (e g., breaking, popping, fracturing, opening, exposing hollow cores thereof) to produce voids in the porous structure. These voids of the individual hollow glass bodies may open into one another to form porous cavities that extend and interconnect through the overall porous structure and may open to surfaces thereof. The high surface area of the porous structures disclosed herein may be provided by a secondary phase, which may include nanosized inorganic particles having a surface area of greater than or equal to 10 m2 / g; nano-sized crystal grains comprising reaction products of a reaction between the silica-containing glass and a coarse inorganic particle having surface area less than 10 m2 / g; or a combinations of these.

[0081] The present disclosure is further directed to batch compositions for making the porous structures. The batch compositions for making the porous structures may comprise at least the hollow glass bodies and a secondary phase precursor. The secondary phase precursor may be the nano-sized inorganic particles having surface area greater than or equal to 10 m2 / g, the coarse inorganic particles having surface area of less than 10 m2 / g, or a combination ofboth. The coarse inorganic particles may be oxides, hydroxides, salts, or combinations thereof of alkali metals and / or alkaline earth metals and may be reactive with the glass of the hollow glass bodies at temperatures of from 800 °C to 1000 °C to form the nano-sized crystal grains having high surface area. The present disclosure is also directed to a CO2 capture devices comprising the porous structures disclosed herein and one or more adsorbents applied to the surfaces of the porous structures.

[0082] The porous structures disclosed herein have both high surface area of greater than or equal to 5 m2 / g, and high porosity, such as greater than or equal to 50% porosity. Additionally, the porous structures, after firing, may have a composition comprising constituents that can enhance the performance of alkaline sorbents, such as but not limited to PEI, ME A, DEA, PPI, PPA, etc., loaded onto the porous structure. In particular, the composition of the porous structure may include at least one magnesium-based crystal phase, such as but not limited to forsterite, clinoenstatite, and / or diopside. Additionally or alternatively, in embodiments, the composition of the porous structure may also include one or more calcium-based crystal phases, such as but not limited to wollastonite, pseudowollastonite, Kilchoanite , cristobalite, or combinations of these. Additionally or alternatively, in embodiments, the composition of the porous structures may further include one or more of roedderite, corundum, zirconia, and glass. One or more of these phases in the composition of the porous structures may enhance performance of the adsorbents loaded thereon. Without intending to be bound by any particular theory, it is believed that the high surface area of greater than or equal to 5 m2 / g of the porous structures may promote greater distribution of the adsorbents, which may increase the CO2 accessibility to the adsorbent, thereby increasing the adsorption performance. Further, the compositions of the honeycomb-shaped porous structures disclosed herein may have low firing temperature, such as peak firing temperatures of less than about 1000 °C, less than about 950 °C, or even less than about 900 °C compared to conventional cordierite honeycombs, which are fired at temperatures greater than about 1400 °C.

[0083] The porous structures may be utilized as substrates for CO2 capture applications. The high surface area of greater than or equal to 5 m2 / g for the porous structures may enable the carbon dioxide adsorbents to be applied directly to the surfaces of the porous structure without first applying an interlayer.

[0084] Refernng now to FIG. 1 , one embodiment of a porous structure 1 12 disclosed herein comprising a ceramic honeycomb is schematically depicted. The porous structure 112 may bea "honeycomb" in that the porous structure 112 may include elongate channels 212 that extend generally through at least a portion of the porous structure 112, such as extending linearly from an outer surface 214 (e.g., face) of the porous structure 112 to or near an opposing outer surface of the porous structure 112. In embodiments, some or all of the elongate channels 212 may be open on both ends, which may allow fluids (e.g., CO2 containing gases, desorption gases, etc.) to flow through the elongate channels 212. In embodiments, the porous structure 112 may include plugs (not shown) in the ends of one or more of the elongate channels, where the plugs force the fluids to flow through walls and webs of the porous structure. The plugs may force fluid flow from one channel, through the pores in the walls of the porous structure, and into another adjacent channel. Flow of the fluid through the pores of the porous structure may provide greater contact of the fluids, such as CO2 containing gas, with adsorbents contained within the pores of the porous structure. In still other embodiments, the porous structure 112 may be porous but not include elongate channels 212 so that the CO2 containing gas passes through the pores of the porous structure.

[0085] Referring again to FIG. 1, when present, the elongate channels 212 may have relatively high aspect ratios, such as length-to-width ratio or length-to-diameter ratio, where length L is oriented along (i.e., parallel to) the flow path of the elongate channels 212 between openings on the outer surface 214 provided by the elongate channels 212 on opposing outer surfaces 214 of the porous structure 1 12, as shown in FIG. 1. The elongate channels 212 are elongate such that the aspect ratio, defined as the length of an elongate channel 212 in relation to widest cross-sectional dimension of the respective elongate channel 212 orthogonal to the length L (e.g., L divided by the diameter of the channel for channels having circular crosssections), of at least some of (e.g., most. >90%, all) the channels is greater than or equal to 10, greater than or equal to 20, greater than or equal to 50, greater than or equal to 100, and less than or equal to 50,000. The elongate channels 212 may have any convenient cross-sectional shape, such as square as shown in FIG. 1, circular as shown in FIG. 3, or any other convenient shape.

[0086] Referring now to FIG. 2, in embodiments, the porous structure 112 may have a square or rectangular cross-sectional shape rather than the circular cross-sectional shape shown in FIG. 1. While FIGS. 1 and 2 show a porous structure 112 having a generally cylindrical geometry, other geometries are contemplated, such as cube, box, sheet, or more complex geometries. According to embodiments, the porous structure 112 may be highly porous, and the pores (e.g., cavities, voids, space between structures) are open to one another such that fluids may passthrough the pores, into and through the porous structure 112. However, the porous structure 112 may be only semi-permeable, in some such embodiments, allowing only some fluids to pass through the porous structure 112, but trapping or blocking others.

[0087] The porous structures may be produced from a batch composition comprising at least the hollow glass bodies and at least one secondary phase precursor. The batch compositions further may include a liquid vehicle and an organic system. The organic system may include one or more binders, additives, etc. The batch compositions of the present disclosure may be formed into green structures and then fired to produce the porous structures. The green structures may refer to pre-fired or pre-sintered structures made from the batch composition before firing and / or sintering. The green structures may be exterior walls and / or interior walls or web of a porous structure, such as a honeycomb-shaped porous structure 112 as shown in FIG. 1.

[0088] Follow firing of the green structures, the porous structures may comprise from 5 wt.% to 95 wt.% glass, crystallized glass, or both and from 5 wt.% to 95 wt.% of the secondary phase based on the total weight of the porous structure. The glass, crystallized glass, or both may comprise a silica-containing glass composition. The hollow glass bodies and the secondary phase may be sintered together, and at least a portion of the hollow glass bodies may be breached. Voids defined within the individual breached hollow glass bodies may open into one another to form cavities that extend through the porous structure and to outer surfaces thereof. The porous structure has greater than or equal to 50% porosity by volume and a surface area greater than or equal to 5 m2 / g.

[0089] In embodiments, the porous structures 112, in terms of weight, may comprise a significant proportion of glass, crystallized glass, or both, such as at least 25% of the weight, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or even at least 95% by weight glass, crystallized glass, or both based on the total weight of the porous structure. Such large portions of the porous structures 112 formed from glass and / or crystallized glass of the hollow glass bodies may be surprising or counterintuitive for those in industry' because they may expect such structures to be particularly fragile and / or not hold together at all.

[0090] In embodiments, the porous structures 112 may comprise from about 5 wt.% to about 95 wt.% of the glass from the hollow glass bodies, based on the total weight of the porous structure 112, such as from about 5 wt.% to about 75 wt.%. from about 5 wt.% to about 60wt.%, from about 5 wt.% to about 55 wt.%, from about 5 wt.% to about 50 wt.%, from about 5 wt.% to about 45 wt.%, from about 5 wt.% to about 40 wt.%, from about 5 wt.% to about 35 wt.%, from about 5 wt.% to about 30 wt.%, from about 5 wt.% to about 25 wt.%, from about 5 wt.% to about 20 wt.%, from about 10 wt.% to about 95 wt.%, from about 10 wt.% to about 75 wt.%, from about 10 wt.% to about 60 wt.%, from about 10 wt.% to about 55 wt.%, from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 45 wt.%, from about 10 wt.% to about 40 wt.%, from about 10 wt.% to about 35 wt.%, from about 10 wt.% to about 30 wt.%, from about 10 wt.% to about 25 wt.%, from about 10 wt.% to about 20 wt.%. from about 15 wt.% to about 95 wt.%, from about 15 wt.% to about 75 wt.%, from about 15 wt.% to about 60 wt.%, from about 15 wt.% to about 55 wt.%, from about 15 wt.% to about 50 wt.%, from about 15 wt.% to about 45 wt.%, from about 15 wt.% to about 40 wt.%, from about 15 wt.% to about 35 wt.%, from about 15 wt.% to about 30 wt.%, from about 15 wt.% to about 25 wt.%, from about 15 wt.% to about 20 wt.%, from about 20 wt.% to about 95 wt.%. from about 20 wt.% to about 75 wt.%, from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 30 wt.%, from about 20 wt.% to about 25 wt.%, or any subrange therebetween, of the glass from the hollow glass bodies, based on the total weight of the porous structure.

[0091] In embodiments, the porous structures 112 may comprise from about 5 wt.% to about 95 wt.% of the secondary phase, based on the total weight of the porous structure 112, such as from about 5 wt.% to about 75 wt.%, from about 5 wt.% to about 60 wt.%, from about 5 wt.% to about 55 wt.%, from about 5 wt.% to about 50 wt.%, from about 5 wt.% to about 45 wt.%, from about 5 wt.% to about 40 wt.%. from about 5 wt.% to about 35 wt.%, from about 5 wt.% to about 30 wt.%, from about 5 wt.% to about 25 wt.%, from about 5 wt.% to about 20 wt.%, from about 10 wt.% to about 95 wt.%, from about 10 wt.% to about 75 wt.%, from about 10 wt.% to about 60 wt.%, from about 10 wt.% to about 55 wt.%, from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 45 wt.%, from about 10 wt.% to about 40 wt.%, from about 10 wt.% to about 35 wt.%, from about 10 wt.% to about 30 wt.%, from about 10 wt.% to about 25 wt.%, from about 10 wt.% to about 20 wt.%, from about 15 wt.% to about 95 wt.%, from about 15 wt.% to about 75 wt.%, from about 15 wt.% to about 60 wt.%, from about 15 wt.% to about 55 wt.%, from about 15 wt.% to about 50 wt.%, from about 15 wt.% to about 45 wt.%, from about 15 wt.% to about 40 wt.%. from about 15 wt.% to about 35 wt.%. from about 15 wt.% to about 30 wt.%, from about 15 wt.% to about 25 wt.%, from about 15 wt.% to about20 wt.%, from about 20 wt.% to about 95 wt.%, from about 20 wt.% to about 75 wt.%, from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%. from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 30 wt.%. from about 20 wt.% to about 25 wt.%, or any subrange therebetw een, of the secondary phase based on the total w eight of the porous structure.

[0092] In embodiments, the secondary' phase may comprise the nano-sized inorganic particles having a surface area of greater than or equal to 10 m2 / g. During the firing process, the nano-sized inorganic particles may remain generally unchanged and may provide a high surface area structure embedded in the surfaces of the glass from the hollow glass bodies. In embodiments, the secondary phase precursor may be the coarse inorganic particles, and the secondary phase may comprise the reaction products of a reaction between the silica-containing glass of the hollow glass bodies and the coarse inorganic particle having surface area less than 10 m2 / g and containing oxides, hydroxides, salts, or combinations thereof of alkali metals and / or alkaline earth metals. The reaction between the silica-containing glass and the coarse inorganic particles may produce nano-sized crystal grains having surface area greater than about 10 m2 / g. The nano-sized crystal grains may comprise one or more crystalline phase, such as but not limited to forsterite, clinoenstatite, diopside, wollastonite, pseudowollastonite, Kilchoanite, cristobalite, roedderite, corundum, other secondary crystal phase, or combinations of these. In embodiments, the secondary phase may comprise both the nano-sized inorganic particles having a surface area of greater than or equal to 10 m2 / g and nano-sized crystal grains comprising reaction products of a reaction between the silica-containing glass of the hollow glass bodies and the coarse inorganic particles having surface area less than 10 m2 / g.

[0093] As previously discussed, the batch compositions disclosed herein for making the porous structures may comprise at least the plurality of hollow glass bodies and a secondary phase precursor. The hollow glass bodies may comprise a silica-containing glass. In embodiments, the batch composition may further include at least one liquid vehicle and an organic system. The organic system may comprise one or more binders, one or more additives, or combinations of these.

[0094] The batch compositions disclosed herein include the hollow glass bodies. Hollow bodies and hollow glass bodies may be used interchangeably throughout the present specification. The batch composition of the present disclosure and the porous structures madetherefrom may include and / or be at least partially formed from a plurality of hollow glass bodies, where a "plurality" of hollow glass bodies may refer to greater than or equal to 100, or even greater than or equal to 1,000 hollow glass bodies. The hollow glass bodies may act as both a pore former and a main frame structure to provide high porosity to the porous structure. The hollow glass bodies may include a glass shell that encloses a hollow volume. The hollow volume may comprise a gas, such as but not limited to air or other gas. The hollow glass bodies may have various shapes. The hollow glass bodies may be generally spherical or may have an irregular shape, such as having a potato-shape for example.

[0095] The hollow glass bodies can be characterized by diameter, where the "diameter" may refer to the diameter of the hollow body if the volume of the hollow body was arranged in aperfect spherical geometry. The size of hollow glass bodies may be selected and characterized based on the diameter, where a "D50" particle size corresponds to a 50% pass point of hollow glass bodies having a diameter of the D50 value, where half in a group are larger and half are smaller in diameter than the D50 value. The hollow glass bodies may have a D50 of greater than or equal to 1 pm, greater than or equal to 3 pm, greater than or equal to 5 pm, or even greater than or equal to 10 pm. The hollow glass bodies may have a D50 of less than or equal to 100 pm, less than or equal to 50 pm, or even less than or equal to 40 pm. The hollow glass bodies may have a D50 of from 1 pm to 100 pm, 1 pm to 50 pm, from 1 pm to 40 pm, from 3 pm to 100 pm. from 3 pm to 50 pm. from 3 pm to 40 pm, from 5 pm to 100 pm from 5 pm to 50 pm, 5 pm to 40 pm, from 10 pm to 100 pm, from 10 pm to 50 pm, or from 10 pm to 40 pm.

[0096] The D10 value of the hollow glass bodies refers to a 10% pass point of the hollow bodies, where only 10% of the hollow bodies have a diameter less than the D10 value. The D90 value of the hollow glass bodies refers to a 90% pass point of the hollow glass bodies, where 90% of the hollow glass bodies have a diameter less than the D90 value. The D10 and D90 values for the hollow glass bodies may be used to evaluate the particle size distribution of the hollow glass bodies. The particle size distribution of the hollow glass bodies may be generally characterized by the expression (D90-D10) / D50. The hollow glass bodies may have a particle size distribution of less than or equal to 2, less than or equal to 1.5, less than or equal to 1, less than or equal to 0.8. less than or equal to 0.4, less than or equal to 0.2, less than or equal to 0. 1, or less than or equal to 0.06, where the size distribution is defined as the quotient of (D90-D10) / D50. In embodiments, the composition may include two or more different ty pes or sizes of hollow glass bodies. In these embodiments, each type or size of hollow glass bodiesmay be characterized by a D50 value and a particle size distribution such that the particle size distribution for the hollow glass bodies overall in the composition is multi-modal.

[0097] The hollow glass bodies incorporated into the composition and before firing (i.e., before breaching the hollow glass bodies, as discussed further herein) may have a density of greater than or equal to about 0. 1 g / cm3, such as greater than or equal to about 0.3 g / cm3, where the density is the mass per volume, which includes the interior bubble volume of the hollow glass bodies. The hollow glass bodies incorporated into the composition and before firing may have a density of less than or equal to about 1.5 g / cm3, such as less than or equal to about 1.0 g / cm3, or even less than or equal to about 0.7 g / cm3. The hollow glass bodies before firing may have a density of from about 0.1 g / cm3to about 1.5 g / cm3. from about 0.1 g / cm3to about 1.0 g / cm3, from about 0. 1 g / cm3to about 0.7 g / cm3, from about 0.3 g / cm3to about 1.5 g / cm3, from about 0.3 g / cm3to about 1.0 g / cm3, or from about 0.3 g / cm3to about 0.7 g / cm3.

[0098] The hollow glass bodies may have a wall thickness of the shell sufficient to enable the hollow glass bodies to withstand being formed into green structures, such as through extrusion or molding, but thin enough to enable breaching of a majority of the hollow glass bodies during firing. The hollow glass bodies may have an average wall thickness of from about 0.2 pm to about 10 pm, or from about 1 pm to about 3 pm.

[0099] The hollow glass bodies may have an isostatic crush strength that is sufficient so that the hollow glass bodies do not break during the forming process, such as during extrusion. The isostatic crush strength of the hollow glass bodies depends on the shell thickness, particle size, and glass composition of the hollow glass bodies. In embodiments, particularly resilient hollow glass bodies may be used, such as those having a mean isostatic crush strength of at least 1000 psi (6.9 MPa), such as at least 2000 psi (13.8 MPa), such as at least 3000 psi (20.7 MPa) (see Measuring Isostatic Pressing Strength of Hollow Glass Microspheres by Mercury - inj ection Apparatus by Yun and Shou, Key Engineering Materials, vol. 544. pp. 460-5 (2013)).

[0100] The hollow glass bodies may include glass (e.g., consist of, consist mostly of by volume, comprise). In embodiments, the hollow glass bodies may comprise, consist essentially of, or consist of a silica-containing glass, such as but not limited to silica glass, soda lime glass, borosilicate glass, aluminosilicate glass, or other glasses. In embodiments, the hollow bodies may comprise, consist essentially of, or consist of silica-containing glass microspheres. The glass of the hollow glass bodies may be fully amorphous. In embodiments, the glass of the hollow glass bodies may be amorphous prior to heating, and subsequently may devitrify and / orcrystallize during the firing process. For clarity, "glass" as used herein includes amorphous glass and / or at least partially devitrified glass with cry stals.

[0101] According to embodiments, hollow glass bodies with high crystallinity at softening temperatures of the hollow glass bodies, such as hollow glass bodies including more than 45% silica (SiCh) and / or CaSiOs. etc. by weight, facilitate transformation processes from internal porosity to open connected porosity, as discussed below. The glass composition constituents may include more than 50 wt.% SiCh, such as from 50 wt.% to 85 wt.%, from 50 wt.% to 80 wt.%, from 74 wt.% to 85 wt.% SiCh, or from 74 wt.% to 80 wt.% SiCh based on the total weight of the glass. In embodiments, the glass of the hollow glass bodies may additionally include more than about 6.5% CaO, less than about 7% and at least some B2O3. less than about 1% and at least some AI2O3, at least some Fe2O3, less than 2.5%, and at least some Na2O, and / or at least some K2O. In embodiments, the glass of the hollow glass bodies may comprise MgO, such as from 0 wt.% to 15 wt.% MgO. In embodiments, the glass of the hollow glass bodies is, is mostly, or includes soda lime glass, borosilicate glass, and / or aluminum silicate glass. Some exemplary glass compositions and corresponding attributes of various hollow glass bodies are provided in Tables 1 and 2. Hollow glass bodies with different compositions may also be used to similar effect.

[0102] Table 1: Exemplary' hollow glass body compositions

[0103] Table 2: Attributes of hollow glass bodies

[0104] In embodiments, the batch compositions may include a plurality of different types of hollow glass bodies, such as hollow glass bodies having different glass compositions or different physical attributes. The different physical attributes may include different median or average particle sizes, different softening temperatures, different particle size distributions, different densities, different shell thicknesses, different crush strengths, or combinations of these. In embodiments, the batch compositions may include first hollow glass bodies and second hollow glass bodies, where the second glass bodies have one or more of a glass composition, median or average particle size, softening temperature, particle size distribution,density, shell thickness, crush strength, or combinations of these, that is different from the first hollow glass bodies.

[0105] The batch compositions of the present disclosure may include an amount of the hollow glass bodies sufficient to produce a porous structure having a porosity of greater than or equal to 50%, greater than or equal to 60%. or even greater than or equal to 70%. In embodiments, the compositions may include from 50 vol.% to 99 vol.% hollow glass bodies, where the volume percentage refers to the true volume of the hollow glass bodies, including the internal volume within the shell, divided by the combined true volume of the hollow glass bodies and the secondary- phase precursor (e.g., not including the water, binder, or additives). The true volume of the hollow glass bodies refers to the volume of the hollow glass bodies comprising the shell and internal volume defined by the shell, but not including the interstitial spaces between the hollow glass bodies. The true volume of the secondary phase precursors refers to a volume of the particles excluding the inter-particulate and intra-particulate spaces in a powder. The batch compositions may include from about 50 vol.% to about 95 vol.%. from about 50 vol.% to about 85 vol.%, from about 50 vol.% to about 75 vol.%, from about 60 vol.% to about 99 vol.%, from about 60 vol.% to about 95 vol.%, from about 60 vol.% to about 90 vol.%, from about 60 vol.% to about 85 vol.%, from about 60 vol.% to about 75 vol.%, from about 75 vol.% to about 99 vol.%, or from about 75 vol.% to about 95 vol.% hollow glass bodies, where the volume percentage refers to the true volume of the hollow glass bodies, including the internal volume within the shell, divided by the combined true volume of the hollow glass bodies and the true volume of the secondary- phase precursor.

[0106] The batch compositions may include from about 5 wt.% to about 95 wt.% hollow glass bodies, where the weight percentage is based on the total weight of the hollow glass bodies and the secondary- phase precursors. The batch compositions may include from about 5 wt.% to about 90 wt.%, from about 5 wt.% to about 80 wt.%, from about 5 wt.% to about 70 wt.%, from about 25 wt.% to about 95 wt.%, from about 25 wt.% to about 90 wt.%, from about 25 wt.% to about 80 wt.%, from about 25 wt.% to about 70 wt.%, from about 50 wt.% to about 90 wt.%, from about 50 wt.% to about 80 wt.%, or from about 50 wt.% to about 70 wt.% hollow glass bodies based on the total weight of the hollow glass bodies and the secondary phase precursors. In embodiments, the batch composition may include from 5 wt.% to 95 wt.% hollow glass bodies based on the total weight of the batch composition (e.g., including the liquid vehicle and organic system in addition to the hollow glass bodies and secondary- phase precursors), such as from 5 wt.% to 90 wt.%, from 5 wt.% to 80 wt.%. from 5 wt.% to 50 wt.%,from 5 wt.% to 40 wt.%, from 5 wt.% to 35 wt.%, from 10 wt.% to 95 wt.%, from 10 wt.% to 90 wt.%, from 10 wt.% to 80 wt.%, from 10 wt.% to 50 d.%, from 10 wt.% to 40 wt.%, from 10 wt.% to 35 wt.%, from 20 wt.% to 95 wt.%, from 20 wt.% to 90 wt.%, from 20 wt.% to 80 wt.%, from 20 wt.% to 50 wt.%, from 20 wt.% to 40 wt.%, or from 20 wt.% to 35 wt.% hollow glass bodies based on the total weight of the batch composition.

[0107] The secondary phase precursors are solid inorganic particulate materials that are not a glass. In embodiments, the secondary phase precursor may comprise nano-sized inorganic particles having a high surface area. The nano-sized inorganic particles may have a melt temperature greater than the softening temperature of the glass of the hollow glass bodies. The nano-sized inorganic particles may have a surface area of greater than or equal to about 10 m2 / g. In embodiments, the nano-sized inorganic particles may have a surface area greater than or equal to about 20 m2 / g, greater than or equal to about 50 m2 / g, greater than or equal to about 100 m2 / g, greater than or equal to about 150 m2 / g, or even greater than or equal to about 200 m2 / g. In embodiments, the nano-sized inorganic particles may have a surface area of from about 10 m2 / g to about 1000 m2 / g, such as from about 10 m2 / gto about 900 m2 / g, from about 20 m2 / g to about 1000 m2 / g, from about 20 m2 / g to about 900 m2 / g, from about 50 m2 / g to about 1000 m2 / g, from about 50 m2 / g to about 900 m2 / g, from about 100 m2 / g to about 1000 m2 / g, from about 150 m2 / g to about 1000 m2 / g, or from about 200 m2 / g to about 1000 m2 / g. The nanosized inorganic particles may have a median particle size in a range that allows for the nanosized inorganic particles to be distributed across the surfaces of the glass phase after firing. In embodiments, the nano-sized inorganic particles may have a median particle size (d50) of from about 0.1 nanometers to about 100 nanometers, such as from about 0.5 nanometers to about 100 nanometers, or from about 1 nanometer to about 100 nanometers.

[0108] The nano-sized inorganic particles may be unreactive or have very low reactivity with the glass of the hollow glass bodies during firing at the temperature less than or equal to the peak firing temperatures. Thus, after firing, the nano-sized inorganic particles may remain chemically and physically the same as they were before the firing. When the secondary phase precursor is the nano-sized inorganic particles, the nano-sized inorganic particles, in their original form, may become the secondary phase. The nano-sized inorganic particles may comprise one or more of gamma alumina (y-AhOs), zirconia, zeolite, magnesium oxide, silica, cerium oxide (CeCh), titanium oxide (TiCh), or any combination thereof. In embodiments, the nano-sized inorganic particles may be selected from the group consisting of gamma alumina, zirconia, zeolite, magnesium oxide, silica. CeCh, TiCh, and any combinations thereof. Inembodiments, the nano-sized inorganic particles may comprise gamma alumina. The nanosized inorganic particles may act as a rigid frame member, which can reduce the flowability7of the softened hollow glass bodies when heated above the softening temperature of the hollow glass bodies. The nano-sized inorganic particles may be capable of maintaining their original particle shape at temperatures greater than the softening temperature of the hollow glass bodies. In embodiments, the nano-sized inorganic particles may be able to maintain their original shape at temperatures greater than or equal to 500 °C, or even greater than or equal to 800 °C, such as from about 500 °C to about 1000 °C.

[0109] In embodiments, the secondary phase precursor may include coarse inorganic particles having lower surface area compared to the nano-sized inorganic particles. The coarse inorganic particles may be reactive with the glass of the hollow glass bodies during firing to produce nano-sized crystal grains comprising one or more secondary cry stalline phases and having a high surface area, such as a surface area of greater than 10 m2 / g. In particular, the coarse inorganic particles can include inorganic materials that may act as a crystallizing agent, a reactive agent, or both, and may interact and / or react with the glass of the hollow glass bodies to form ne v crystal phase(s) at temperatures less than the softening temperatures of the hollow glass bodies by themselves. These new cry stal phases may comprise the nano-sized crystal grains having increased surface area compared to the starting coarse inorganic particles and / or hollow glass bodies. The nano-sized crystal grains comprising these new secondary crystal phases may have an average surface area greater than or equal to 10 m2 / g, or even greater than or equal to 20 m2 / g. Additionally, the formation of these neyv crystal phases at lesser temperatures can suppress shrinkage during the cry stallization phase of firing. In particular, the new crystal phases of the nano-sized crystal grains may retain their shape at temperatures greater than the softening temperature of the hollow glass bodies and, once formed, may act as rigid bodies that may hinder or impede the floyv of the remaining amorphous glass yvhen heated above the softening temperature of the glass. Hindering the flow of the glass may reduce firing shrinkage of the green structures made from the compositions herein

[0110] The coarse inorganic particles may comprise alkali metal salts, alkali metal oxides, alkali metal hydroxides, alkaline earth metal salts, alkaline earth metal oxides, alkali earth metal hydroxides, or any combinations thereof. In embodiments, the coarse inorganic particles may comprise one or more of MgO, Mg(OH)2, CaO, Ca(OH)2, Cas(PO4)2, CaCOs, Li2O, Li2CC>3, Li2BO3, Na2O, NaOH, Na2CC>3, K2O, KOH, K2CO3, or any combination thereof. In embodiments, the coarse inorganic particles may be selected from the group consisting ofMgO, Mg(OH)2, CaO, Ca(OH)2, Ca3(PO4)2, CaCO3, Li2O, LI2CO3, Li2BO3, Na2O, NaOH, Na2CO3, K2O, KOH, K2CO3, and any combination thereof. In embodiments, the coarse inorganic particles may comprise MgO.

[0111] The coarse inorganic particles may have a surface area less than about 10 m2 / g, less than or equal to 8 m2 / g, or even less than or equal to 5 m2 / g. The coarse inorganic particles may comprise a surface area greater than 0 (zero) m2 / g to 10 m2 / g, such as from greater than 0 m2 / g to 8 m2 / g, from greater than 0 m2 / g to 5 m2 / g, from 0.1 m2 / g to 10 m2 / g, from 0.1 m2 / g to 8 m2 / g, or from 0. 1 m2 / g to 5 m2 / g. The coarse inorganic particles may have a median particle size (D50) of from about 100 nanometers (nm) to about 100 micrometers (pm), such as from about 100 nm to about 50 pm. from about 100 nm to about 1 pm. from about 500 nm to about 100 pm, from about 500 nm to about 50 pm, from about 500 nm to about 1 pm, or from about 1 pm to about 100 pm.

[0112] In embodiments, the secondary phase precursors in the batch compositions may comprise a combination of both the nano-sized inorganic particles and the coarse inorganic particles. When the secondary phase precursors include both the nano-sized inorganic particles and the coarse inorganic particles, the secondary phase produced after firing may comprise a combination of the nano-sized inorganic particles and the nano-sized crystal grains, which result from reaction between the coarse inorganic particles and the silica-containing glass of the hollow glass bodies. In embodiments, the secondary phase precursors in the batch composition may comprise one or more t pes of nano-sized inorganic particles selected from the group consisting of gamma alumina, zirconia, zeolites, magnesium oxide, silica, CeCh, T1O2. and any combinations thereof and one or more types of coarse inorganic particles selected from the group consisting of MgO, Mg(OH)2, CaO, Ca(OH)2, Ca3(PO4)2, CaCO3, LJ2O, Li2CO3, Li2BO3, Na2O, NaOH, Na2CO3. K2O, KOH, K2CO3, and any combinations thereof. In embodiments, the secondary phase precursors may comprise a combination of gamma alumina and MgO.

[0113] The batch compositions disclosed herein may include a total amount of the secondary phase precursors sufficient to produce a porous structure having a surface area after firing of greater than or equal to 5 m2 / g, greater than or equal to 10 m2 / g, or even greater than or equal to 20 m2 / g. In embodiments, the batch compositions may comprise from 5 vol.% to 50 vol.% of the secondary phase precursors, wherein the volume percentages are based on the total bulk volume of inorganic solid components of the composition (i.e., the hollow glassbodies and the secondary phase precursors). When the concentration of secondary phase precursor in the batch compositions is too low, such as less than about 5 vol.%, the porous structure may not have sufficient surface area. When the concentration of the secondary phase precursors is too great, the porous structure may have reduced porosity, such as a porosity of less than 50%. In embodiments, the batch compositions may comprise from 5 vol.% to 45 vol.%, from 5 vol.% to 40 vol.%, from 5 vol.% to 35 vol.%, from 5 vol.% to 30 vol.%, from 5 vol.% to 25 vol.%, from 5 vol.% to 20 vol.%, from 10 vol.% to 50 vol.%, from 10 vol.% to 45 vol.%, from 10 vol.% to 40 vol.%, from 10 vol.% to 35 vol.%, from 10 vol.% to 30 vol.%, from 10 vol.% to 25 vol.%, from 10 vol.% to 20 vol.%, from 15 vol.% to 50 vol.%, from 15 vol.% to 45 vol.%, from 15 vol.% to 40 vol.%, from 15 vol.% to 35 vol.%, from 15 vol.% to 30 vol.%, from 15 vol.% to 25 vol.%, from 15 vol.% to 20 vol.%, from 20 vol.% to 50 vol.%, from 20 vol.% to 45 vol.%, from 20 vol.% to 40 vol.%, from 20 vol.% to 35 vol.%, from 20 vol.% to 30 vol.%. or from 20 vol.% to 25 vol.% of the secondary phase precursors, wherein the volume percentages are based on the total bulk volume of inorganic solid components of the composition. In embodiments, the batch compositions may comprise from about 15 vol.% to about 35 vol.% of the secondary phase precursors based on the total bulk volume of inorganic solid components of the composition. In embodiments, the batch compositions may comprise about 20 vol.% of the secondary phase precursors based on the total bulk volume of inorganic solid components of the composition.

[0114] On a weight basis, the batch compositions may include from about 5 wt.% to about 95 wt.% of the secondary phase precursors, where the weight percentage is based on the total weight of the hollow glass bodies and the secondary phase precursors. The batch compositions may include from about 5 wt.% to about 90 wt.%, from about 5 wt.% to about 80 wt.%. from about 5 wt.% to about 70 wt.%, from about 25 wt.% to about 95 wt.%, from about 25 wt.% to about 90 wt.%, from about 25 wt.% to about 80 wt.%, from about 25 wt.% to about 70 wt.%, from about 50 wt.% to about 90 wt.%, from about 50 wt.% to about 80 wt.%, or from about 50 wt.% to about 70 wt.% of the secondary phase precursors based on the total weight of the hollow glass bodies and the secondary phase precursors. In embodiments, the batch composition may include from 5 wt.% to 95 wt.% secondary phase precursors based on the total w eight of the batch composition (e.g., including the liquid vehicle and organic system in addition to the hollow glass bodies and secondary- phase precursors), such as from 5 wt.% to 90 wt.%. from 5 wt.% to 80 wt.%, from 5 wt.% to 50 wt.%, from 5 wt.% to 40 wt.%. from 5 wt.% to 35 wt.%, from 10 wt.% to 95 wt.%, from 10 wt.% to 90 wt.%, from 10 wt.% to 80wt.%, from 10 wt.% to 50 wt.%, from 10 wt.% to 40 wt.%, from 10 wt.% to 35 wt.%, from 20 wt.% to 95 wt.%, from 20 wt.% to 90 wt.%, from 20 wt.% to 80 wt.%, from 20 wt.% to 50 wt.%, from 20 wt.% to 40 wt.%, or from 20 wt.% to 35 wt.% of the secondary phase precursors based on the total weight of the batch composition.

[0115] In embodiments, the secondary phase precursors may include both nano-sized inorganic particles and coarse inorganic particles. In these embodiments, the batch compositions may comprise from about 5 vol.% to about 25 vol.% of the nano-sized inorganic particles, and from about 5 vol.% to about 25 vol.% of the coarse inorganic particles, based on the total bulk volume of inorganic solid components of the composition.

[0116] The secondary phase precursors may be provided as a dry powder or may be provided in the form of a dispersion or suspension of the secondary phase precursors in a liquid solvent. In embodiments, the secondary phase precursors may be provided as a dispersion or suspension of the secondary phase precursors in a solvent, which may further, optionally, include a dispersant. The weight percentages and volume percentages discussed herein are based on the weight of the secondary phase precursors itself without the solvent and / or dispersant.

[0117] The batch compositions may further include an organic system. The organic system may include one or more binders, additives, or combinations thereof. In embodiments, the batch compositions disclosed herein may include one or more binders. A binder is used to bond particles together to form the green structure that can hold a honeycomb shape or other shape until the green structure can be fired. The binder can be any kind of cellulose or cellulose derivatives. The binder can also be a polymer binder, such as but not limited to polyvinyl alcohol (PVA) polymers, polyvinylpyrrolidone (PVP) polymers, or other polymers or combinations of polymers. In embodiments, the batch compositions may include a binder that comprises cellulose, cellulose derivatives, polymer binders, or combinations thereof. In embodiments, the binder may include methylcellulose, carboxymethyl cellulose (CMC), or combinations thereof. In embodiments, the batch compositions may include one or more binders selected from the group consisting of methylcellulose, CMC, PVA, PVP, and combinations thereof. In embodiments, the composition may include from 5 wt.% to 20 wt.% binder based on the combined weight of the hollow glass bodies and the secondary’ phase precursors in the batch composition (i.e., (weight of binder ( / ((weight of hollow glass bodies)+(weight of secondary phase precursors))).

[0118] In embodiments, the batch compositions may include one or more additives, such as but not limited to a slip agent and / or lubricant, such as oil or sodium stearate. In embodiments, the additives may act as rheology modifiers to make the batch composition easier to extrude, increase the extrusion rate, and improve the quality of the porous structures, in particular honeycomb-shaped porous structures. In embodiments, the additives may include sintering aids, such as but not limited to sodium stearate or other sintering aids. In embodiments, the additives may include a pore former, such as an organic pore former, such as a starch (e.g., com starch, pea starch, etc.). The additives can be sodium stearate, oil, graphite, starch, other additives, or combinations of these. In embodiments, the batch composition may comprise one or more additives selected from the group consisting of sodium stearate, oil, graphite, starch, and combinations of these. The batch compositions may include from greater than 0 wt.% to 5 wt.% additives, such as from 0. 1 wt.% to 5 wt.% additives based on the based on the combined weight of the hollow glass bodies and the secondary phase precursors. In embodiments, the batch composition may not include additives. In embodiments, the composition may not include sodium stearate or other sintering aids. In embodiments, the composition may not include a pore former, such as starch.

[0119] The batch compositions may include a liquid vehicle. The liquid vehicle may be water, one or more alcohols, or any combination thereof. In embodiments, the liquid vehicle is water. The amount of the liquid vehicle in the batch composition may be sufficient to enable the batch composition to be extruded or otherwise shaped or formed into the green structure but not so much that the green structure is unable to maintain its shape after formation. The batch compositions may include from about 25 wt.% to about 100 wt.% or from about 30 wt.% to about 70 wt.% of the liquid vehicle based on the combined weight of the hollow glass bodies and the secondary phase precursors.

[0120] In embodiments, the batch density (e.g.. ‘‘wet batch’7density) of the batch composition may be less than or equal to 1.5 g / cm3, such as less than or equal to 1.0 g / cm3, less than or equal to 0.5 g / cm3, or even less than or equal to 0.3 g / cm3. The batch density of the batch composition may be greater than or equal to 0.1 g / cm3. In embodiments, the green structures and batch material comprising the batch composition may float in water (i.e. specific gravity less than 1, compared to water), while the finished porous structures, after firing and / or breaching of the hollow glass bodies, may sink in water.

[0121] The batch compositions of the present disclosure comprising the hollow glass bodies and the secondary phase precursors may have a peak firing temperature less than the peak firing temperature of batch compositions having only the hollow glass bodies. The batch compositions of the present disclosure may have peak firing temperatures of less than or equal to about 1000 °C, less than or equal about 950 °C, less than or equal to about 900 °C, or even less than or equal to about 850 °C. The batch compositions disclosed herein may have a peak firing temperature of from about 500 °C to about 1000 °C, from about 500 °C to about 950 °C, from about 500 °C to about 900 °C, from about 500 °C to about 850 °C, from about 500 °C to about 800 °C, from about 600 °C to about 1000 °C, from about 600 °C to about 950 °C, from about 600 °C to about 900 °C, from about 600 °C to about 850 °C, from about 600 °C to about 800 °C, from about 800 °C to about 1000 °C, from about 800 °C to about 970 °C, from about 800 °C to about 950 °C, from about 800 °C to about 900 °C, from about 850 °C to about 1000 °C. from about 850 °C to about 970 °C, from about 850 °C to about 950 °C, or from about 900 °C to about 1000 °C.

[0122] The porous structures disclosed herein may be prepared from the batch compositions according to a method that includes preparing the batch composition, forming a green structure from the composition, and firing the green structure at a temperature less than or equal to 1000 °C. Firing the green structure bonds the hollow glass bodies and the secondary phase precursor together and breaches at least a portion of the hollow glass bodies to form the porous structure. When the secondary phase precursor comprises the coarse inorganic particles, the firing may also cause reactions between the glass of the hollow glass bodies and the coarse inorganic particles to produce the nano-sized cry stal grains having high surface area (e g., >10 m2 / g). The resulting porous structures may have a porosity of greater than or equal to 50%, and an average surface area of greater than or equal to 5 m2 / g.

[0123] Preparing the batch compositions may include combining the hollow glass bodies, the secondary phase precursors, liquid vehicle, and organic system (e.g., binders and / or additives). The batch compositions may any of the constituents and may have any of the properties previous described herein for the batch compositions. The constituents of the batch composition may be combined and mixed according to known methods. The hollow glass bodies, secondary phase precursors, liquid vehicle, binders, and additives may have any of the features, properties, or amounts previously described herein. The average pore size, porosity, surface area, or combinations of these properties of the porous structure may be modified bychanging the constituents and / or relative concentrations of constituents of the batchcompositions. In particular, methods disclosed herein may include tuning an average pore size, porosity, and / or surface area of the porous structure by changing a type of the secondary phase precursors and / or a proportion of the secondary phase precursors to the hollow glass bodies in the batch composition. The average pore size may also be tuned by modifying the peak firing temperature, the hold / dwell time at the peak firing temperature, the temperature ramping rate during heating, or combinations of these. Increasing the peak firing temperature, increasing the hold / dwell time at the peak firing temperature, and decreasing the temperature ramping rate during heating may all increase the average pore size to the extent the whole structure is not completely melted. In embodiments, the methods may include modifying a porosity and / or surface area of the porous structure by changing a type of the secondary phase precursor and / or a relative amount of the secondary phase precursor in the batch composition.

[0124] After preparation of the batch composition, the methods disclosed herein may include forming the green structure from the batch composition. In embodiments, the batch composition may be formed into a green structure having a honeycomb shape having a plurality of elongate channels extending through the green structure (e.g., elongate channels 212 as shown in FIG. 1). Forming the green structure may include extrusion, molding, tape-casting, rolling, calendaring, 3D printing, other forming process, or combinations of these. Extruding the green structures may be particularly efficient for forming through-channels (e.g.. elongate channels 212 as shown in FIG. 1) in porous structures such as the honeycomb-shaped porous structure of FIG. 1, or other regular features in the respective green structures. However, in other contemplated embodiments, such green structures may be molded, tape-cast, or otherwise shaped or processed, which may better or alternatively preserve integrity of the hollow glass bodies. In still other contemplated embodiments, structures with shapes far different from those of porous structures 112, 212 in FIGS. 1 and 2 may be extruded or otherwise formed.

[0125] In embodiments, the batch composition may be extruded to form the green structures. Extrusion may be accomplished using a twin-screw extruder or other suitable extrusion machine. The batch composition comprising the hollow' glass bodies and secondary' phase precursor may be extruded at a rate and pressure to preserve integrity of most (e.g., more than 50%, more than 75%. more than 90%) of the hollow glass bodies. With that said, in other contemplated embodiments, extrusion rate and pressure may preserve integrity of many of the hollow' glass bodies, but not most, such as less than 50%, but at least 25%, or at least 20%. Preserving integrity of the hollow glass bodies may allow the hollow' glass bodies to occupy relatively large volumes of space within the green structures with voids between the hollowglass bodies and within the hollow glass bodies (i.e., the internal volume of the hollow glass bodies). The extrusion rates and pressures may vary7depending upon the size of the hollow7glass bodies, the glass of the hollow glass bodies, and the extruding device. In some embodiments, extrusion pressures may be in the range of less than 2500 psi, such as less than 2000 psi, and / or at least 500 psi.

[0126] Following forming of the green structures from the batch compositions, the methods may include firing the green structures to a peak firing temperature. Conditions and handling of the green structures during the heating is such that adjoining hollow glass bodies may physically interact with one another, such as directly bonding to one another (e.g., sinter, weld, melt-into), but without fully losing their individual structures. Put another way, the conditions and handling during firing are such that the hollow glass bodies do not fully liquefy and do not completely lose structure, and instead become bonded to one another such that, in the aggregate, the resulting porous structure is cohesive and rigid.

[0127] Additionally, in embodiments, the conditions and handling of the green structures during the heating may be such that many of the hollow glass bodies (e.g., most, >90%. >95%, >99%) breach or break, such as by rupture from internal gas expansion and / or by devitrification or otherwise. The green structures may be heated to a point that the hollow glass bodies lose integrity and the glass of the hollow glass bodies shatters or is otherwise breached, but without the hollow glass bodies fully liquefying or completely losing structure. In other contemplated embodiments, the hollow glass bodies may be breached by microwaves, sound, or other phenomena. Breaching the hollow glass bodies contained in the green structures, as disclosed herein, may enable the voids of the hollow glass bodies to be maintained and / or even enlarged and joined to one another to create a porous network within the porous structures.

[0128] In embodiments, the secondary7phase precursors may comprise the nano-sized inorganic particles, and firing the green structure may bond the hollow glass bodies and the nano-sized inorganic particles together and may breach at least a portion of the hollow glass bodies to form the porous structure having the porosity7greater than or equal to 50% and the surface area of greater than or equal to 5 m2 / g. Additionally or alternatively, in embodiments, the secondary7phase precursors may comprise the coarse inorganic particles comprising the oxides, hydroxides, salts, or combinations thereof of alkali metals and / or alkaline earth metals, and firing the green structure causes a reaction between the silica-containmg glass of the hollow glass bodies and the coarse inorganic particles to produce nano-sized crystal grains havinggreater surface area compared to the coarse inorganic particles and may breach at least a portion of the hollow glass bodies to form the porous structure having a porosity' of greater than or 50% and the surface area of greater than or equal to 5 m2 / g.

[0129] In embodiments, during firing, the green structures may be heated, such as by firing the green structures in a furnace, by laser heating the green structures, or other heating methods. The heating may bum out, char, chemically transform, or otherwise influence the binder. In embodiments, the methods may include heating the green structures to at least to a softening temperature of the glass of the hollow glass bodies. But, the hollow glass bodies are not overheated, such as being heated well above a liquidus temperature of the glass, at which temperatures the hollow glass bodies may fully lose cohesion or structure. The methods may include heating the green structures to a peak firing temperature that is at least greater than or equal to a softening temperature of the glass and less than about 1000 °C. When the peak firing temperature is greater than or equal to about 1000 °C, it w as found that the surface area of the finished porous structure greatly decreases. Thus, at peak firing temperatures of greater than or equal to about 1000 °C, a porous structure having a surface area greater than about 5 m2 / g is difficult to obtain. At temperatures below' the softening temperature of the glass, fewer of the hollow glass bodies are breached during firing, leading to low' porosity'. The softening temperature may depend on the glass composition of the hollow glass bodies.

[0130] Depending upon the glass composition and materials in the composition used to make the green structures, the firing the green structures may include heating the green structures to a peak firing temperature of greater than or equal to about 500 °C, greater than or equal to about 600 °C, greater than or equal to about 700 °C, greater than or equal to 750 °C, greater than or equal to 800 °C, or even greater than or equal to 850 °C, and less than or equal to about 1000 °C, less than or equal to about 975 °C. less than or equal to about 950 °C, less than or equal to about 925 °C, even less than or equal to 900 °C. In embodiments, the methods may include heating or firing the green structure to a peak firing temperature of less than or equal to about 1000 °C, such as from 500 °C to 1000 °C, from 500 °C to 975 °C, from 500 °C to 950 °C, from 500 °C to 925 °C. from 500 °C to 900 °C, from 600 °C to 1000 °C, from 600 °C to 975 °C, from 600 °C to 950 °C, from 600 °C to 925 °C, from 600 °C to 900 °C, from 700 °C to 1000 °C, from 700 °C to 975 °C, from 700 °C to 950 °C, from 700 °C to 925 °C, from 700 °C to 900 °C, from 750 °C to 1000 °C, from 750 °C to 975 °C, from 750 °C to 950 °C, from 750 °C to 925 °C, from 750 °C to 900 °C, from 800 °C to 1000 °C, from 800 °C to 975 °C, from 800 °C to 950 °C, from 800 °C to 925 °C, from 800 °C to 900 °C, from 825 °C to1000 °C, from 825 °C to 975 °C, from 825 °C to 950 °C, from 825 °C to 925 °C, from 825 °C to 900 °C, from 850 °C to 1000 °C, from 850 °C to 975 °C, from 850 °C to 950 °C, from 850 °C to 925 °C, from 850 °C to 900 °C, from 900 °C to 1000 °C, or any range or subrange between each of these temperatures.

[0131] In embodiments, firing the green structures may include conducting a firing process to systematically heat the green structure to the peak firing temperature. In embodiments, the firing process may include heating the green structure to the peak firing temperature at a generally constant temperature ramping rate of from about 50 °C per hour to about 300 °C per hour, holding the green structures at the peak firing temperature for a time of from 1 hour to 10 hours, and then cooling the green structures back to ambient temperatures. In embodiments, firing the green structure may comprises ramping the green structure to the peak firing temperature that is less than or equal to about 1000 °C, such as from about 500 °C to about 1000 °C, and holding the green structure at the peak firing temperature for a period of from 1 hour to 10 hours.

[0132] In embodiments, firing the green structures may include debinding the batch composition of the green structures. Debinding the green structures may include heating the green structures from ambient temperature to a first temperature(s) (e g., fixed temperature and / or temperatures in a limited range) at a generally constant ramping rate of from 50 °C per hour to about 300 °C per hour. The first temperature may be in a debind temperature range for the batch composition. The debind temperature range may be from 200 °C to 400 °C or from 300 °C to 400 °C. The first temperature is less than a lower crystallization temperature of the glass of the hollow glass bodies, which is the temperature at which crystallization of the glass begins. The green bodies may be held at the first temperature for a first dwell time, which maybe at least 1 minute, such as from 1 minute to 10 hours or from 1 hour to 10 hours . Alternatively or additionally, in embodiments, at the first temperature, the temperature ramping rate may be reduced to a temperature ramping rate of less than 50 °C per hour, less than or equal to 20 °C per hour, less than 10 °C per hour, or even less than 5 °C per hour. The temperature ramping rate may be maintained at the lower temperature ramping rate until the upper debind temperature of around 400 °C is reached, at which point the temperature ramping rate may be returned to the first ramping rate of from 50 °C per hour to 300 °C per hour. In embodiments, the firing process for firing the green structures to produce the porous structure may not include debinding the composition of the green structure.

[0133] In embodiments, the temperature may be increased to a second temperature(s). The second temperature may be in a cry stallization range of the glass, such as a temperature greater than the lower crystallization temperature and less than the upper crystallization temperature of the glass of the hollow glass bodies. The second temperature may be greater than 400 °C, such as from 500 °C to 800 °C. The green structures may be held at the second temperature for a second dwell time of at least 1 minute, such as from 1 hour to 10 hours. In embodiments, during the firing process, the temperature is increased from the second temperature(s) to a third temperature(s) with a third dwell time, such as where the second temperature is above 400 °C and below a softening point of glass of the hollow glass bodies and the third temperature is above the softening point of the glass of the hollow glass bodies. The third temperature may be the peak firing temperature. The third dwell time may be at least 1 minute, such as from 1 hour to 10 hours.

[0134] In embodiments, firing the green structures may include heating the green structure to a de-bind temperature of from 200 °C to 400 °C and maintaining the green structure at the de-bind temperature for a de-bind dwell time. The de-bind dwell time may be from 1 hour to 10 hours. In embodiments, firing the green structures may not include a de-bind dwell time and the temperature of the green structures may be ramped continuously through the de-bind temperature range. Firing the green structures may further include ramping the temperature of the green structure to the lower crystallization temperature of the hollow glass bodies at a first ramping rate of from greater than 100 °C per hour to 250 °C per hour. At the lower crystallization temperature of the hollow glass bodies, firing may include slowing the temperature ramp rate to a second ramping rate of less than 100 °C per hour or holding the temperature of the green structures at a temperature between the lower crystallization temperature of the glass and the upper crystallization temperature of the glass for a time period of from 1 hour to 10 hours. Slowing the temperature ramping rate in the crystallization temperature range or holding the green structure at a temperature in the crystallization temperature range may reduce shrinkage of the porous structure compared to the green structure, as will be described in further detail herein. Firing the green structures may further include ramping the temperature of the green structures to the peak firing temperature of the green structure and maintaining the green structure at the peak firing temperature for a period of from 1 hour to 10 hours. The firing process converts the green structures to the porous structures disclosed herein.

[0135] Following firing the green structures to the peak firing temperature and holding the green structures at the peak firing temperature for a period of time to produce the porous structures, the porous structures may be cooled back to ambient temperature. The methods disclosed herein for making the porous structures may comprise cooling the porous structure back to ambient temperature following firing at the peak firing temperature. In embodiments, the methods may include cooling the porous structures to a temperature that is at least 100 °C less than the temperatures to which the green structures were heated during firing (i.e., peak firing temperature). In embodiments, the methods may include cooling the porous structures to a temperature less than 100 °C or even less than 50 °C, such as a temperature of from 20 °C to 100 °C, or from 20 °C to 50 °C. During the cooling, the adjoining hollow glass bodies, which may be less spherical at this point, are and / or remain physically bonded to one another, such as directly or indirectly bonded. Indirect boding may refer to adjacent hollow glass bodies being bonded to each other through an intermediate bonding agent, such as the nano-sized inorganic particles, the nano-sized crystal grains produced from the coarse inorganic particles, unreacted coarse inorganic particles, residue of the binder added to the composition, or combinations of these.

[0136] In embodiments, cooling the porous structures may include dwelling the porous structures at temperatures greater than the ambient temperatures but less than the firing temperatures. In embodiments, cooling the porous structures may include dwelling the porous structures at an annealing temperature of the glass of the hollow glass bodies. Dwelling may occur at incremental steps, in some embodiments, or may be in the form of very gradual temperature declines within certain temperature ranges in other embodiments, both of which may allow for formation of crystals in the materials of the hollow glass bodies and / or may facilitate relaxing of residual stresses by annealing.

[0137] In embodiments, the methods disclosed herein may further include modifying an average surface area of the porous structure. Modifying the average surface area of the porous structure may comprise changing a concentration of the secondary7phase precursors in the batch composition, changing the type of the secondary phase precursors in the batch composition, changing the firing temperature of the green structures, or combinations of these.

[0138] The porous structures produced from the batch compositions, green structures, and firing process may comprise the hollow glass bodies and the secondary phase that are sintered together. The porous structures produced from the batch compositions may comprise primarilythe constituents from the glass of the hollow glass bodies and the secondary phase. The porous structures may also include small amounts of binder or compounds resulting from firing the binder and other additives. At least a portion of the hollow glass bodies in the porous structure are breached. In embodiments, the porous structure may have greater than or equal to 50%, greater than or equal to 70%, greater than or equal to 80%, or even greater than or equal to 90% and less than or equal to 100% of the hollow glass bodies are breached. The voids defined within the individual breached hollow glass bodies may open into one another to form cavities that extend through the porous structure and to outer surfaces thereof.

[0139] Follow firing of the green structures, the porous structures may comprise from 5 wt.% to 95 wt.% glass, crystallized glass, or both and from 5 wt.% to 95 wt.% of the secondary phase based on the total w eight of the porous structure. The glass, crystallized glass, or both may comprise the constituents of the silica-containing glass composition of the hollow^ glass bodies. In embodiments, the porous structures, in terms of weight, may comprise a significant proportion of glass, crystallized glass, or both, such as at least 5%, at least 25% of the weight, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or even at least 95%, by weight glass, crystallized glass, or both based on the total weight of the porous structure. Such large portions of the porous structures 112 formed from glass and / or crystallized glass may be surprising or counterintuitive for those in industry because they may expect such structures to be particularly fragile and / or not hold together at all. In embodiments, the porous structures may comprise greater than or equal to 5 wt.%, greater than or equal to 25 wt.%, greater than or equal to 40 wt.%, greater than or equal to 50 wt.%, or even greater than or equal to 60 wt.% silica glass, crystallized silica glass, or both based on the total weight of the porous structure. The porous structures may comprise less than or equal to 95 wt.%, less than or equal to 90 wt.%, less than or equal to 80 wt.%, less than or equal to 70 wt.%, or even less than or equal to 60 wt.% silica glass, crystallized silica glass, or both based on the total weight of the porous structure. The porous structures may comprise from 5 wt.% to 95 wt.%, from 25 wt.% to 90 wt.%, from 25 wt.% to 80 wt.%, from 25 wt.% to 70 wt.%, from 25 wt.% to 60 wt.%, from 25 wt.% to 50 wt.%, from 25 wt.% to 40 wt.%, from 40 wt.% to 90 wt.%, from 40 wt.% to 80 wt.%, from 40 wt.% to 70 wt.%, from 40 wt.% to 60 wt.%, from 50 wt.% to 90 wt.%, from 50 wt.% to 80 wt.%, from 50 wt.% to 70 wt.%, from 60 wt.% to 90 wt.%, from 60 wt.% to 80 wt.%, or from 60 wt.% to 70 wt.% silica glass, crystallized silica glass, or both based on the total weight of the porous structure.

[0140] At least some of the glass of the hollow glass bodies may be devitrified to form crystallized silica glass having one or more crystal phases. The cry stal phases of the cr stallized silica glass may include constituents from the secondary phase precursor, particularly when the secondary phase precursor comprises the coarse inorganic particles. Gradually heating and dwelling the green structures at the peak firing temperature, as disclosed herein, may facilitate crystal growth in the silica glass of the hollow glass bodies. The crystallized silica glass may increase the strength of the porous structures compared to non-crystallized amorphous glass. While the batch composition of the green structures may include amorphous hollow glass bodies, the porous structures after firing may be glass-ceramics with crystallinity' greater than or equal to 45% by weight (wt.%), such as greater than or equal to 50 wt.%, greater than or equal to 60 wt.%, greater than or equal to 70 wt.%, greater than or equal to 80 wt.%, greater than or equal to 90 wt.%, or even greater than or equal to 95 wt.% cry stallinity based on the total weight of the porous structure. The weight percentage of the crystalline phases and residual glass phase is determined based on x-ray diffraction (XRD) using a Rietveld analysis. The XRD specta were obtained using a D8 ENDEAVOR™ XRD machine available from Bruker and equipped with Cu radiation. The Rietveld analysis based on the XRD spectra were performed using the TOP AS™ version 6 analysis software from Bruker. In embodiments, the porous structures may comprises an amorphous glass phase. In embodiments, the porous structure may comprise less than 55 wt.%, less than 50 wt.%, or even less than 36 wt.% amorphous phase glass based on the total weight of glass in the porous structure. In embodiments, the porous structure may include from 1 wt.% to 55 wt.%, from 5 wt.% to 50 wt.%, from 5 wt.% to 36 wt.%, from 10 wt.% to 55 wt.%, from 10 wt.% to 50 wt.%, or from 10 wt.% to 36 wt.% amorphous-phase glass based on the total weight of the porous structure.

[0141] In embodiments, the porous structures may comprise from about 5 wt.% to about 95 wt.% of the secondary' phase, based on the total weight of the porous structure, such as from about 5 wt.% to about 75 wt.%, from about 5 wt.% to about 60 wt.%, from about 5 wt.% to about 55 wt.%, from about 5 wt.% to about 50 wt.%, from about 5 wt.% to about 45 wt.%, from about 5 wt.% to about 40 wt.%, from about 5 wt.% to about 35 wt.%, from about 5 wt.% to about 30 wt.%, from about 5 wt.% to about 25 wt.%, from about 5 wt.% to about 20 wt.%, from about 10 wt.% to about 95 wt.%, from about 10 wt.% to about 75 wt.%, from about 10 wt.% to about 60 wt.%, from about 10 wt.% to about 55 wt.%, from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 45 wt.%. from about 10 wt.% to about 40 wt.%. from about 10 wt.% to about 35 wt.%, from about 10 wt.% to about 30 wt.%, from about 10 wt.% to about25 wt.%, from about 10 wt.% to about 20 wt.%, from about 1 wt.% to about 95 wt.%, from about 15 wt.% to about 75 wt.%, from about 15 wt.% to about 60 wt.%, from about 15 wt.% to about 55 wt.%, from about 15 wt.% to about 50 wt.%. from about 15 wt.% to about 45 wt.%, from about 15 wt.% to about 40 wt.%, from about 15 wt.% to about 35 wt.%. from about 15 wt.% to about 30 wt.%, from about 15 wt.% to about 25 wt.%, from about 15 wt.% to about 20 wt.%, from about 20 wt.% to about 95 wt.%, from about 20 wt.% to about 75 wt.%, from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 30 wt.%, from about 20 wt.% to about 25 wt.%, or any subrange therebetween, of the secondary phase based on the total weight of the porous structure.

[0142] As previously discussed, the secondary' phase may comprise the nano-sized inorganic particles, the nano-sized crystal grains formed from reaction of the coarse inorganic particles and the silica glass, or a combination of both. In embodiments, the secondary phase may comprise the nano-sized inorganic particles having a surface area of greater than or equal to 10 m2 / g. During the firing process, the nano-sized inorganic particles may remain generally unchanged and may provide a high surface area structure embedded in the surfaces of the glass from the hollow glass bodies. In embodiments, the porous structures may comprise from about 5 wt.% to about 95 wt.%, from about 5 wt.% to about 75 wt.%, from about 5 wt.% to about 60 wt .%, from about 5 wt.% to about 55 wt.%, from about 5 wt.% to about 50 wt.%, from about 5 wt.% to about 45 wt.%, from about 5 wt.% to about 40 wt.%, from about 5 wt.% to about 35 wt.%, from about 5 wt.% to about 30 wt.%, from about 5 wt.% to about 25 wt.%, from about 5 wt.% to about 20 wt.%, from about 10 wt.% to about 95 wt.%, from about 10 wt.% to about 75 wt.%, from about 10 wt.% to about 60 wt.%, from about 10 wt.% to about 55 wt.%, from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 45 wt.%, from about 10 wt.% to about 40 wt.%, from about 10 wt.% to about 35 wt.%, from about 10 wt.% to about 30 wt.%, from about 10 wt.% to about 25 wt.%, from about 10 wt.% to about 20 wt.%. from about 15 wt.% to about 95 wt.%, from about 15 wt.% to about 75 wt.%, from about 15 wt.% to about 60 wt.%, from about 15 wt.% to about 55 wt.%, from about 15 wt.% to about 50 wt.%, from about 15 wt.% to about 45 wt.%, from about 15 wt.% to about 40 wt.%, from about 15 wt.% to about 35 wt.%, from about 15 wt.% to about 30 wt.%, from about 15 wt.% to about 25 wt.%, from about 15 wt.% to about 20 wt.%, from about 20 wt.% to about 95 wt.%. from about 20 wt.% to about 75 wt.%, from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%,from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%, from about 20 wt.% to about 40 wt.%. from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 30 wt.%, from about 20 wt.% to about 25 w t.%, or any subrange therebetween, of the nano-sized inorganic particles based on the total weight of the porous structure.

[0143] In embodiments, the secondary phase precursor may be the coarse inorganic particles, and the secondary phase may comprise the nano-sized crystal grains, which are the reaction products of the reaction between the silica-containing glass of the hollow glass bodies and the coarse inorganic particle. The reaction between the silica-containing glass and the coarse inorganic particles may produce the nano-sized crystal grains comprising one or more secondary crystalline phases. The secondary crystalline phases of the nano-sized crystal grains may include, but are not limited to, forsterite, clinoenstatite, diopside, wollastonite, pseudowollastonite, Kilchoanite, cristobalite, roedderite, corundum, zirconia, other secondary crystal phase, or combinations of these. In embodiments, the nano-sized crystal grains may comprise at least at least one magnesium-based crystal phase selected from forsterite, clinoenstatite, diopside, or combinations thereof. In embodiments, the nano-sized crystal grains may comprise at least one calcium-based crystal phase selected from wollastonite, pseudo wollastonite, kilchoanite, crostobalite, or combinations thereof. In embodiments, the nanosized crystal grains may comprise one or more crystalline phases selected from roedderite, corundum, zirconia, or combinations of these.

[0144] In embodiments, the porous structures may comprise from about 5 wt.% to about 95 wt.%, from about 5 wt.% to about 75 wt.%, from about 5 wt.% to about 60 wt.%, from about 5 wt.% to about 55 wt.%, from about 5 wt.% to about 50 wt.%, from about 5 wt.% to about 45 wt.%, from about 5 wt.% to about 40 wt.%, from about 5 wt.% to about 35 wt.%, from about 5 wt.% to about 30 wt.%, from about 5 wt.% to about 25 wt.%, from about 5 wt.% to about 20 wt.%, from about 10 wt.% to about 95 wt.%. from about 10 wt.% to about 75 wt.%. from about 10 wt.% to about 60 wt.%, from about 10 wt.% to about 55 wt.%, from about 10 wt.% to about 50 wt.%, from about 10 wt.% to about 45 wt.%, from about 10 wt.% to about 40 wt.%, from about 10 wt.% to about 35 wt.%, from about 10 wt.% to about 30 wt.%, from about 10 wt.% to about 25 wt.%, from about 10 wt.% to about 20 wt.%. from about 15 wt.% to about 95 wt.%, from about 15 wt.% to about 75 wt.%, from about 15 wt.% to about 60 wt.%, from about 15 wt.% to about 55 wt.%, from about 15 wt.% to about 50 wt.%, from about 15 wt.% to about 45 wt.%, from about 15 wt.% to about 40 wt.%, from about 15 wt.% to about 35 wt.%, from about 15 wt.% to about 30 wt.%, from about 15 wt.% to about 25 wt.%, from about 15 wt.% to about20 wt.%, from about 20 wt.% to about 95 wt.%, from about 20 wt.% to about 75 wt.%, from about 20 wt.% to about 60 wt.%, from about 20 wt.% to about 55 wt.%, from about 20 wt.% to about 50 wt.%, from about 20 wt.% to about 45 wt.%. from about 20 wt.% to about 40 wt.%, from about 20 wt.% to about 35 wt.%, from about 20 wt.% to about 30 wt.%. from about 20 wt.% to about 25 wt.%, or any subrange therebetween, of the nano-sized crystal grains based on the total weight of the porous structure.

[0145] In embodiments, the secondary phase may comprise both the nano-sized inorganic particles having a surface area of greater than or equal to 10 m2 / g and nano-sized crystal grains comprising reaction products of a reaction between the silica-containing glass and the coarse inorganic particles.

[0146] The porous structures may have a high porosity’ of greater than or equal to about 50% as determined by mercury intrusion porosimetry, as discussed herein. In embodiments, the porous structures may have a porosity’ of greater than or equal to about 55%, greater than or equal to about 60%, or even greater than or equal to about 65% as determined by mercury intrusion porosimetry. In embodiments, the porous structures may have a porosity of from about 50% to about 80%, from about 50% to about 75%, from about 50% to about 70%. from about 50% to about 65%, from about 55% to about 80%, from about 55% to about 75%, from about 55% to about 70%, from about 55% to about 65%, from about 60% to about 80%, from about 60% to about 75%, from about 60% to about 70%, from about 60% to about 65%, or from about 65% to about 80%. The porosity’ may be modified by changing the amount of the secondary phase precursor in the batch composition. In embodiments, the batch composition for making the porous structure may have less than or equal to 50 vol.%, less than or equal to 25 vol.%, or even less than or equal to 12.5 vol.% secondary' phase precursors, based on the total bulk volume of inorganic solid components of the composition (i.e. , hollow glass bodies and secondary phase precursors), in order to provide a porosity of greater than 50%, such as from 50% to 80%.

[0147] The porous structures may have a total volume, within outer surfaces thereof (see, e.g., outer surface having the openings on outer surface 214 of FIG. 2), of at least about 1 cubic centimeter (cm3), such as at least about 2 cm3, such as at least about 10 cm3, such as at least about 50 cm3, and / or no more than about 2000 cm3, such as no more than about 1000 cm3. In embodiments, the total volume may be much larger than 2000 cm3, such as for large frontal area filters.

[0148] As previously discussed, the porous structures disclosed herein may have a specific surface area of greater than or equal to about 5 m2 / g. In embodiments, the porous structures may have a specific surface area of greater than or equal to about 10 m2 / g, or even greater than or equal to about 20 m2 / g. The specific surface area of the porous structures may be determined by the Brunauer-Emmett-Teller (BET) surface area analysis using N2 adsorption. To determine the specific surface area, samples of the porous structures are prepared by heating at 300 °C while simultaneously evacuating under vacuum for 4 hours to remove any impurities. The prepared samples are then cooled with liquid nitrogen and analyzed by measuring the volume of gas adsorbed at specific pressures using a TRISTAR™ II 3020 surface area and porosity analyzer from Micromeritics. The N2 adsorption isotherms generated by the surface area and porosity analyzer are then analyzed using the BET method to determine the specific surface area of the porous structures. In embodiments, the porous structure may have a specific surface area of from about 5 m2 / g to about 350 m2 / g, from about 5 m2 / g to about 250 m2 / g. from about 5 m2 / g to about 200 m2 / g, from about 5 m2 / g to about 100 m2 / g, from about 5 m2 / g to about 90 m2 / g, from about 5 m2 / g to about 80 m2 / g, from about 5 m2 / g to about 50 m2 / g, from about 10 m2 / g to about 350 m2 / g, from about 10 m2 / g to about 250 m2 / g, from about 10 m2 / g to about 200 m2 / g, from about 10 m2 / g to about 100 m2 / g. from about 10 m2 / g to about 90 m2 / g. from about 10 m2 / g to about 80 m2 / g, from about 10 m2 / g to about 50 m2 / g, from about 20 m2 / g to about 350 m2 / g, from about 20 m2 / g to about 250 m2 / g, from about 20 m2 / g to about 200 m2 / g, from about 20 m2 / g to about 100 m2 / g, from about 20 m2 / g to about 90 m2 / g, from about 20 m2 / g to about 80 m2 / g, from about 20 m2 / g to about 50 m2 / g, from about 30 m2 / g to about 350 m2 / g, from about 30 m2 / g to about 250 m2 / g, from about 30 m2 / g to about 200 m2 / g, from about 30 m2 / g to about 100 m2 / g, from about 30 m2 / g to about 90 m2 / g, from about 30 m2 / g to about 80 m2 / g, or from about 30 m2 / g to about 50 m2 / g. The average surface area of the porous structure may be modified by changing the amount or type of the secondary phase precursors, increasing or decreasing the peak firing temperature during firing of the green structures, or combinations of these.

[0149] The porous structures of the present disclosure may have a median pore size of from 1 pm to 50 pm, from 1 pm to 20 pm, from 1 pm to 16 pm, from 2 pm to 50 pm, from 2 pm to 20 pm. from 2 pm to 16 pm, from 5 pm to 50 pm, from 5 pm to 20 pm, from 5 pm to 16 pm, from 8 pm to 50 pm, from 8 pm to 20 pm, from 8 pm to 16 pm, from 12 pm to 50 pm, from 12 pm to 20 pm, or from 12 pm to 16 pm. The median pore size may refer to a d50 value, which corresponds to a 50% pore size of a porous structure, as measured by mercury intrusionporosimetry, as discussed herein. The median pore size can be tunable by adjusting the packing pattern of hollow glass bodies and particles of the inorganic powder. The combination of the hollow glass bodies with an inorganic powder may enable a broader range of pore size distribution for the porous structures herein compared to porous structures made with only the hollow glass bodies and no inorganic powder. The median pore size can be tuned in the range of from 1 pm to 50 pm.

[0150] The porous structure may have a pore size distribution characterized by a D-factor. The D-factor of the porous structure is defined to be equal to the quotient (dso-dioj / dso. The dso value refers to a median pore diameter of the porous structure at which 50% by volume of the open porosity of the porous structure has been intruded by mercury during a porosimetry measurement made according the methods disclosed herein. The quantity dio, as used herein, is the pore diameter at which 10% of the pore volume is comprised of pores with diameters smaller than the value of dio. The dio value of the porous structure is equal to the pore diameter at which 90% by volume of the open porosity of the porous structure has been intruded by mercury during a porosimetry measurement. In embodiments, the porous structures including the hollow glass bodies and inorganic powder may have a pore size distribution (dso-dioj / dso of from about 0.1 to about 1.0, such as from about 0.1 to about 0.9, from about 0.1 to about 0.8, from about 0.2 to about 1, from about 0.2 to about 0.9, from about 0.2 to about 0.8, from about 0.3 to about 1.0. from about 0.3 to about 0.9. from about 0.3 to about 0.8, from about 0.4 to about 1, from about 0.4 to about 0.9, from about 0.4 to about 0.8, from about 0.5 to about 1, from about 0.5 to about 0.9, of from about 0.5 to about 0.8.

[0151] The porous structures made from the batch composition comprising the hollow glass bodies and the secondary phase precursors may exhibit less than or equal to 15%, less than or equal to 10%, less than or equal to 8%, less than or equal to 5%, less than or equal to 2, or even less than or equal to 1% shrinkage compared to a green structure comprising the batch composition prior to firing. In embodiments, the porous structure may have a size and shape that are within 15%, within 10%, within 8 %, within 5%, within 2% or even within 1% of a size and shape of a green structure comprising the batch composition prior to firing. The reduced shrinkage may also enable improved control of the fired ware geometry and may decrease substrate defects resulting from shrinkage, among other features.

[0152] In embodiments, the porous structures may have a honeycomb shape comprising a plurality of elongate channels extending through at least a portion of the porous structure, aspreviously described in relation to FIG. 1. The porous structures may have a cell density (i.e., number of elongate channels per unit cross-sectional area) of greater than or equal to 50 cells per square inch (cpsi), such as greater than or equal to 100 cpsi, greater than or equal to 200 cpsi, or greater than or equal to 300 cpsi. The porous structures may have a cell density of less than or equal to 400 cpsi.

[0153] Each of the elongate channels may be separated by cell walls. As previously discussed, the strength of the porous structures made with the hollow glass bodies and secondary phase precursors may enable the web thickness (i.e., thickness of the walls between elongate channels of a honeycomb shaped porous structure) of the porous structure to be reduced. The porous structures disclosed herein may have a web thickness of less than or equal to 10 mils (i.e. thousandths of an inch), such as no more than 8 mils, such as no more than 7 mils, such as no more than 6 mils, such as no more than 5 mils. The porous structures disclosed herein may have a web thickness of from 2 mils to 10 mils, from 2 mils to 8 mils, from 2 mils to 7 mils, from 2 mils to 6 mils, or from 2 mils to 5 mils. In embodiments, the porous structures may have a combination of cell density and web thickness (i.e., noted as: (cell density in cpsi) / (web thickness in mils)) of about 200 / 8. In other embodiments, the porous structures may have combinations of cell density and web thickness of 400 / 7, 400 / 6, 400 / 5, 400 / 4, 400 / 3, 400 / 2, 300 / 7, 300 / 6. 300 / 5, 300 / 4, 300 / 3, 300 / 2, 200 / 7, 200 / 6, 200 / 5, 200 / 4, 100 / 8, 100 / 7, 1 0 / 6, 100 / 5. 50 / 8. 50 / 7. or 50 / 6, where left of the "7” is the cell density in cpsi and to the right of the ‘7” is the web thickness in mils. In embodiments, the porous structure may have a honeycomb shape having a cell density of less than 400 cells per inch and a web thickness between cells of from 2 mils to 8 mils.

[0154] In embodiments, the porous structures may have a cylindrical geometry and may- have a diameter of greater than or equal to 2 inches, greater than or equal to 4 inches, greater than or equal to 6 inches, greater than or equal to 8 inches, greater than or equal to 12 inches, or greater than or equal to 24 inches. The diameter of the porous structure may be less than or equal to 64 inches or less than or equal to 36 inches. In embodiments, the porous structure may have a generally square, rectangular, or other polygonal geometry- in cross-section, with sides of greater than or equal to 2 inches, greater than or equal to 4 inches, greater than or equal to 6 inches, greater than or equal to 8 inches, greater than or equal to 12 inches, or greater than or equal to 24 inches. The sides of the porous structure may be less than or equal to 64 inches or less than or equal to 36 inches. Other contemplated embodiments have other sizes or shapes.

[0155] As previously discussed, the porous structures disclosed herein may be used as substrates for CO2 capture applications. In CO2 capture applications, one or more CO2 adsorbents may be deposited onto the surfaces of the porous structures and / or into the cavities of the porous substrate to produce a CO2 capture device. Referring now to FIG. 3, one embodiment of a CO2 capture device 300 comprising the porous structures 1 12 disclosed herein is schematically depicted. In embodiments, the CO2 capture device 300 may comprise the porous structure 112 having the plurality' of channels 212 extending therethrough. The porous structure 112 may have any of the compositions, properties, or characteristics previously discussed for the porous structure. The CO2 capture device 300 may further include at least one CO2 adsorbent 302 bonded onto surfaces 218 of the porous structure 112 and / or into cavities of the porous structure 112.

[0156] The CO2 adsorbents 302 may include, but are not limited to, one or more of polyethyleneimine (PEI), monoethanolamine (MEA), diethanolamine (DEA), poly(propylenimine) (PPI), phenylpropanolamine (PPA), NaOH, Na2COs, NaHCCE, KOH, K2CO3, KHCO3, or combinations thereof. In embodiments, the CO2 adsorbent 302 may include PEI. The at least one CO2 adsorbent 302 may be bonded directly to the surfaces 218 of the porous structure 112, such as to the surfaces defining the plurality of channels 212 extending through the porous structure 112 and / or to surfaces the cavities of the porous structure 112. The high surface area of greater than or equal to 5 m2 / g of the porous structure 112 may enable the CO2 adsorbents 302 to be directly bonded to the surfaces 218 of the porous structure 112, while providing sufficient surface area of the CO2 adsorbent 302 to efficiently adsorb CO2. In embodiments, the CO2 capture device 300 does not have an interlayer disposed between the surfaces 218 of the porous structure and the CO2 adsorbents bonded thereto.

[0157] The CO2 adsorbents 302 may be applied and bonded to the surfaces 218 of the porous structure 112 by any suitable method, such as but not limited to washcoating, dipcoating, or other known methods. Bonding the CO2 adsorbent 302 to the surfaces 218 of the porous structure does not include applying an interlayer to the surfaces 218 of the porous structure 112 and then applying the CO2 adsorbents 302 to the surface of the interlayer.

[0158] The CO2 capture device 300 comprising the porous structures 112 of the present disclosure may incorporated into a CO2 capture process. In particular, any of the porous structures disclosed herein may be incorporated into a CO2 capture process comprising an adsorption / desorption unit. Referring now to FIG. 4, one embodiment of a system 400 forconducting a CO2 capture process is schematically depicted. The system 400 for CO2 capture may include a gas source 402, a moisture generator 410, a mixing unit 420 downstream of the moisture generator 410, and a test chamber 430 downstream of the mixing unit 420. The gas source 402 may be a source of compressed dry air. The compressed dry air may be divided into two streams. One stream may be passed to the moisture generator 410 and the second stream may be passed directly to the mixing unit 420. The moisture generator 410 may be operable to increase the moisture content of the compressed dry air to produce a compressed air stream 412 having moisture content greater than that of the compressed dry air. The compressed air stream 412 and the second portion of the compressed dry air may be mixed in the mixing unit 420 to produce a mixed gas stream 422, which may be passed to the test chamber 430. The test chamber 430 may include a vessel 432 and the CO2 capture device 300 disposed within the vessel 432. The CO2 capture device 300 may include the porous structure having any of the compositions, features, or properties previously described herein for the porous structures. The test chamber 430 may have an outlet 436 and a vent 438.

[0159] The porous structures disclosed herein may have high surface area, such as surface area greater than or equal to 5 m2 / g, greater than or equal to 10 m2 / g, or even greater than or equal to 20 m2 / g, which may enable the CO2 adsorbents to be bonded directly to the porous structures without an interlayer. The porosity of the porous structures disclosed herein may enable a greater amount of active sorbent material for CO2 to be loaded into the adsorption / desorption unit per unit volume of honeycomb-shaped porous structure. Enabling a greater amount of sorbent material for CO2 to be loaded per unit volume may enable a greater CO2 adsorption capacity per unit volume for the adsorption / desorption unit compared to other types of porous media. The porous structures of the present disclosure may also have lower thermal mass compared to normal cordierite structures, which may reduce energy consumption of the CO2 capture process by reducing the energy needed to heat the porous structure during CO2 desorption compared to normal cordierite structures. Additionally, the porous structures disclosed herein may be less expensive compared to normal cordierite based honeycomb structures typically used in CO2 capture processes. In embodiments, a CO2 capture process may include an adsorption / desorption unit and the porous structure may be integrated into the adsorption / desorption unit.

[0160] Construction and arrangements of the porous structures, assemblies, and structures, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible(e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present inventive technology.TESTMETHODS

[0161] Modulus of Rupture

[0162] Mechanical strength of the porous structures can be evaluated using a 4-point bending point bending test conducted according to ASTM Cl 161. In conducting the mechanical strength testing herein, the samples are cut into 0.25 inch by 0.5 inch by 3 inch minibars. The 4-point bending test is accomplished using a 2 inch support span.

[0163] Porosimetry

[0164] Porosity, median pore volume, and pore size distribution herein are determined using mercury7intrusion porosimetry performed according to standard test methods known in the art.EXAMPLES

[0165] The embodiments described herein wall be further clarified by the following examples. The following examples illustrate the formation of porous structures using the compositions and methods disclosed herein. The following examples are not intended to be limit the scope of the present disclosure.

[0166] Materials

[0167] The hollow glass bodies used in the Examples of the present disclosure included three types of hollow glass bodies: HN70 hollow glass microspheres and H60 hollow glass microspheres obtained from Zhongke Yali Technology Co., Ltd., China, and C-100-T hollow glass microspheres obtained from Zhongke Huaxing New' Materials Co. Ltd. The glass composition of the hollow glass bodies is provided below in Table 3. The H60 hollow glass microspheres have a true density of around 0.60 g / cm3, the HN70 hollow glass microsphereshave a true density of around 0.7 g / cm3, and the C-100-T hollow glass microspheres have a true densi of around 0.6 g / cm3. Throughout the Examples the abbreviation HGMS may be used to indicate hollow glass microspheres. The same methylcellulose binder and lubricant oil were used in all of the examples, and the liquid vehicle in all of the examples was water.Table 3: Properties of Hollow Glass Microspheres

[0168] Example 1: Porous Structures with Nano-Sized Inorganic Particles (i.e.. Gamma Alumina) as the Secondary Phase Precursor

[0169] In Example 1 , porous structures were prepared using nano-sized inorganic particles (i.e., gamma alumina) as the secondary phase precursor. The batch compositions for making the porous structures of Example 1 are provided in Table 4. The gamma alumina (y-AbCh) used for Example 1 had an initial surface area around 230 m2 / g. which can be used to increase the substrate surface area. The hollow glass bodies for Example 1 were the H60 hollow glassmicrospheres in Table 3. For Example 1, the hollow glass bodies, gamma alumina, methylcellulose binder, lubricant oil, and water were combined to produce a batch composition, which was then extruded into a green structure having a honeycomb shape. The green structures were then fired to produce the porous structures of Example 1 according to the firing processes disclosed herein. The peak firing temperature was varied from 820 °C to 1 120 °C for Samples 1A-1E. Table 4 shows the porosity and surface area of the porous structures of samples 1 A-1E resulting from inclusion of the nano-sized inorganic particles having high surface area (e.g., >100 m2 / g). The best result was obtained at a firing temperature of 820 °C in Sample 1 A, which produced a porous structure having a porosity of 55% and surface area of about 89 m2 / g. As shown in Table 4, when the peak firing temperature increased above 1000 °C, the surface area decreased significantly, while the total porosity7remained unchanged.Table 4

[0170] Referring now to FIGS. 5 A-5E, SEM images of the porous structures of Example 1 (Samples 1A-1E) are provided. As shown in FIGS. 5A-5E, the morphology7of the porous structure changes with increasing firing temperature. As temperature increases, hollow glass microspheres experience increasing softening and opening. It was observed that the surface area decreased with increasing peak firing temperature. Without intending to be bound by any particular theory, it is believed that some of the y-AhCh particles were enclosed by glass phase due to the increased softening and opening of the hollow glass microspheres at the greater peak firing temperatures, which is believed to cause the surface area to be reduced as the peak firing temperature increases. This is supported by FIGS. 5D and 5E. which show a decrease in the definition between particles indicating the glass phase surrounding some of the y-AhCh particles.

[0171] Referring now to FIG. 6, XRD plots for the porous structures of Example 1 (Samples 1A-1E) show the cry stalline phases of the porous structure and demonstrate the change in the crystalline phases of the porous structure as the peak firing temperature increases. At low peak firing temperatures of 820 °C and 920 °C, the main phases are cristobalite and wollastonite , which are crystalline phases resulting from crystallization of the glass from the hollow glass microspheres. At the lower peak firing temperatures, the y-AhOs exhibited no phase change or size change, which results in the greater surface area in Table 4 for Samples 1A and IB. When temperature increases, the albite crystalline phase formed, which is a crystalline phase resulting from reaction between the glass of the hollow glass microspheres and the y-AhCh. Additionally, at the higher temperatures, the porous structures exhibited XRD peaks characteristic of corundum (a-AhCh), which is a crystalline phase resulting from transformation of y-AhCh. Thus, the changes in the cry stal phases with increases peak firing temperature are believed to also contribute to the decreasing surface area with increasing peak firing temperature.

[0172] Referring now to FIG. 7, the pore size distribution for each of the porous structures of Example 1 (Samples 1A-1E) are graphically depicted. As shown in FIG. 7, the pore size distribution has a bimodal pattern indicating the presence of nano-sized pores and micro-sized pores. The nanosized pores are provided by the y-AhCh, which is a high surface area material, and the micro-sized pore are formed by hollow glass microspheres. As the peak firing temperature increases from 820 °C to 1120 °C, the amount of intrusion into the nano-sized pores was also reduced, similar to the surface area. Without being bound by any particular theory, it is believed that this reduction in the nano-sized pores may result from the glass phase covering an increasing portion of the Y-AI2O3 particles, from the increasing formation of albite and corundum crystalline phases, or a combination of both.

[0174] In Example 2, porous structures were prepared using coarse inorganic particles (i.e., MgO particles) as the secondary phase precursor. The batch compositions for making the porous structures of Example 2 are provided in Table 5. The MgO particles used for Example 2 had an initial surface area of less than 5 m2 / g. The hollow glass bodies for Example 2 were the C100T hollow glass microspheres from Table 3. For Example 2, the hollow glass bodies, MgO, methylcellulose binder, lubricant oil, and water were combined to produce a batch composition, which was then extruded into a green structure having a honeycomb shape. The green structures were then fired to produce the porous structures of Example 2 according to the firing processes disclosed herein. The peak firing temperature was varied from 720 °C to 920 °C for Samples 2A-2D. Table 5 provides the porosity and surface area of the porous structures formed from the hollow glass microspheres and the MgO particles. Even though MgO has a very low initial surface area <5m2 / g, the MgO was found to react with the hollow glass microspheres to form new phases with nano-size pores that increase the surface area of the porous structures. The best results were obtained for Sample 2B, which had peak firing temperature of 770 °C, a porosity of 68%, and surface area of 2 m2 / g. While the surface area was not high (e.g., >5 m2 / g), the surface area was greater than the surface area of typical cordierite honeycomb porous structures and porous structures made with the hollow glass bodies and no secondary phase precursor.

[0175] For purposes of comparison, Sample 2E was prepared with the C-100-T hollow glass bodies but without the secondary phase precursor MgO. The porous structure of Sample2E was fired at the peak firing temperature of 770 °C. The composition, porosity, and surface area of the porous structure of Sample 2E are provided in Table 5. As shown in Table 5, the porosity of the porous structure of Sample 2E was slightly greater, but the surface area of 0.2 was an order of magnitude less than the surface area of the porous structure of Sample 2B, which included the MgO and was fired at the same firing temperature of 770 °C. Comparison of the porous structure of Sample 2B to the porous structure of Sample 2E shows that the presence of the secondary' phase precursor can increase the surface area of the porous structure.Table 5

[0176] Referring now to FIGS. 8A-8D, SEM images of the porous structures of Sample 2A-2D are provided. As shown in FIGS. 8A-8D, the morphology of the porous structures of Samples 2A-2D show a very porous structure with opened pores. Referring now to FIGS. 9A- 9D, SEM images at greater resolution are provided to show greater detail on the shape of the particles in the porous structures of Example 2. As shown in FIGS. 9A-9D, the frame structures of the porous structures are very' fine particles.

[0177] Referring now to FIG. 10, XRD plots for the porous structures of Example 2 show the crystalline phases of the porous structure and demonstrate the change in the crystalline phases of the porous structure as the peak firing temperature increases from 570 °C to 920 °C. At the lower peak firing temperatures less than about 720 °C or less, no obvious reaction between the MgO and the glass of the hollow glass microspheres was observed, as indicated by the XRD plots showing primarily magnesia (MgO). As the peak firing temperature is increased to 720 °C and from 720 °C to 920 °C. the new phases diopside and forsterite are formed, indicating reaction between the MgO and the glass of the hollow glass microspheres.

[0178] Referring now to FIG. 11 , the pore size distribution for each of the porous structures of Example 2 (Samples 2A-2D) are graphically depicted. As shown in FIG. 11, the pore size distribution for the porous structures of Example 2 are uni-modal with micro-sized pores. Further, as the peak firing temperature increases, the concentration of micro-sized pores does not change very much.

[0179] Example 3: Porous Structures with a Combination of Nano-Sized Inorganic Particles and Coarse Inorganic as the Secondary Phase Precursors

[0180] In Example 3, porous structures w ere prepared using a combination of the nanosized inorganic particles (i.e., gamma alumina) and coarse inorganic particles (i.e., MgO particles) as the secondary phase precursors. The batch compositions for making the porous structures of Example 2 are provided in Table 6. The gamma alumina (y-AhOs) used for Example 3 had an initial surface area around 230 m2 / g, which can be used to increase the substrate surface area. The MgO particles used for Example 3 had an initial surface area of less than 5 m2 / g. For Samples 3A-3D, the hollow glass bodies were the C100T hollow glassmicrospheres in Table 3, and for Sample 3E-3H, the hollow glass bodies were the HN70 hollow glass microspheres from Table 3.

[0181] For Example 3, the hollow glass bodies, gamma alumina, MgO, methylcellulose binder, lubricant oil, and water were combined to produce the batch compositions, which were then extruded into a green structures having a honeycomb shape. The green structures were then fired to produce the porous structures of Example 3 according to the firing processes disclosed herein. The peak firing temperature was varied from 720 °C to 1020 °C for Samples 3A-3D and from 820 °C to 1070 °C for Samples 3E-3H. Table 6 shows the porosity and surface area of the porous structures of samples 3A-3H resulting from inclusion of the combination of both the nano-sized inorganic particles having high surface area (e.g., >100 m2 / g) and the coarse inorganic particles (i.e., MgO having surface area less than 5 m2 / g). The combination of the gamma alumina and the MgO along with firing temperatures of less than 1000 °C produced honeycomb-shaped porous structures having high porosity of greater than 60% and high surface area of greater than 20 m2 / g. In particular, for the Samples 3A-3D - which included the C100T hollow glass microspheres, 20 vol.% MgO, and 15 vol.% y-AhO? - the best result was obtained at a peak firing temperature of 820 °C, which produced a porous structure of Sample 3B having porosity of 63% and surface area of 23 m2 / g. For the Samples 3E-3F - which included the HN70 hollow glass microspheres, 10 vol.% MgO, and 10 vol.% y-AEOs - the best result was obtained at a peak firing temperature of 920 °C, which produced a porous structure of Sample 3F having porosity of 62% and surface area of 25 m2 / g.Table 6

[0182] Referring now to FIGS. 12A-12D, SEM images of the porous structures of Sample 3A-3D are provided. As shown in FIGS. 12A, at a peak firing temperature of 720 °C, the morphology of the porous structures of Sample 3A is not opened and the porosity of the porous structure of Sample 3A is low. Referring now to FIGS. 12B and 12C, the morphology of the porous structures of Samples 3B and 3C (peak firing temperatures of 820 °C and 920 °C respectively) show the hollow glass bodies opened, resulting in the porosity increasing. Referring now to FIGS. 13A-13D, SEM images at greater resolution are provided to show greater detail on the shape of the particles in the porous structures of Samples 3 A-3D. As shown in FIGS. 13A-13D, the porous structures of Sample 3A-3D show the initial y-AbCh particles and the new formed nano-sized crystal grains, which combine to produce a high surface area, particularly for Samples 3A-3C. As shown in FIG. 13D, when the peak firing temperature is increased to 1020 °C, the glass from the hollow glass microspheres covers the initial y-AbChparticles and newly formed nano-sized crystal grains, which leads to the reduced surface area of less than 1 m2 / g for the porous structure of Sample 3D.

[0183] Referring now to FIGS. 14A-14D, SEM images of the porous structures of Sample 3E-3H are provided. As shown in FIGS. 14A, at a peak firing temperature of 820 °C, the morphology of the porous structures of Sample 3E is not opened and the porosity of the porous structure of Sample 3E is low. Referring now to FIGS. 14B and 14C, the morphology of the porous structures of Samples 3F and 3G (peak firing temperatures of 920 °C and 1020 °C respectively) show the hollow7glass bodies opened, resulting in the porosity increasing. Referring now to FIGS. 15A-15D, SEM images at greater resolution are provided to show greater detail on the shape of the particles in the porous structures of Samples 3E-3H. As shown in FIGS. 15A-15D, the porous structures of Sample 3E-3H show the initial y-AbOs particles and the new formed nano-sized cr stal grains, which combine to produce a high surface area, particularly for Samples 3E-3G. As shown in FIG. 15D, when the peak firing temperature is increased to 1070 °C, the glass from the hollow glass microspheres covers at least a portion of the initial y-AhCh particles and newly formed nano-sized crystal grains, which leads to the reduced surface area of about 4 m2 / g for the porous structure of Sample 3H.

[0184] Referring now to FIG. 16, the pore size distributions for the porous structures of Samples 3A-3D are graphically depicted. At the peak firing temperature of 720 °C, the pore size distribution of the porous structure of Sample 3A exhibits two peaks corresponding to the nano-sized pores of the gamma alumina and the microporous structure provided by initial opening of the hollow glass microspheres. When the peak firing temperature is from 820 °C (Sample 3B) to 1020 °C (Sample 3D), the pore size distributions are also bimodal, indicating the presence of nano-sized pores and micro-sized pores. The nano-sized pores are provided by the y-AbOs, which is a high surface area material, and the micro-sized pores are formed by hollow glass microspheres and MgO. As the peak firing temperature increases from 820 °C to 1120 °C, the amount of intrusion into the nano-sized pores was reduced, which mirrored the reduction in surface area for Samples 3B-3D. Without being bound by any particular theory, it is believed that this reduction in the nano-sized pores may result from the glass phase covering an increasing portion of the y-AbCh particles, from the increasing formation of albite and corundum crystalline phases, or a combination of both.

[0185] Refernng now to FIG. 17, the pore size distributions for the porous structures of Samples 3E-3H are graphically depicted. At the peak firing temperature of 820 °C, the poresize distribution of the porous structure of Sample 3E exhibits three separate peaks corresponding to the nano-sized pores of the gamma alumina (<10 nm), the pores formed by initial opening of the hollow glass microspheres (-3000-5000 nm), and the microporous structure provided through interaction between the hollow glass microspheres and the MgO (-7000-9000 nm). When the peak firing temperature is increased from 920 °C (Sample 3F) to 1070 °C (Sample 3H), the amount of intrusion into the nano-sized pores of the gamma alumina was reduced, which mirrored the reduction in surface area for Samples 3F-3H. Without being bound by any particular theory, it is believed that this reduction in the nano-sized pores may result from the glass phase covering an increasing portion of the Y-AI2O3 particles, from the increasing formation of albite and corundum crystalline phases, or a combination of both. Additionally, the magnitude of the peak corresponding to the initial opening of the hollow glass microspheres decreased and the peak corresponding to the microporous structure produced through interaction between the MgO an the hollow glass microspheres increased. Without being bound by any particular theory, it is believed that the increase in the microporous structures characterized by pore size from about 7000 nm to about 9000 nm reflects increasing interaction between the MgO and the hollow glass microspheres with increasing temperature.

[0186] Examples 4-7: CO2 Adsorption Capacity

[0187] In Examples 4-7, various porous structures were loaded with a CO2 adsorbent and then subjected to a CO2 adsorption test. For Example 4, the porous structure was a cordierite porous structure having a porosity of 55% and a specific surface area of less than 0.5 m2 / g. For Example 5, the porous structure was a low surface area porous structure made from hollow glass microspheres without a secondary phase to increase the surface area and had a porosity of 72% and a specific surface area of less than 1 m2 / g. For Example 6, the porous structure was a high surface area porous structure comprising the hollow glass microspheres and the secondary phase comprising gamma alumina. The porous structure for Example 6 had a porosity of 70% and a specific surface area of 13 m2 / g. For Example 7, the porous structure was a high surface area porous structure comprising the hollow glass microspheres and a secondary phase formed from reaction of coarse inorganic particles (MgO particles) and the glass of the hollow glass microspheres. The porous structure for Example 7 had a porosity of 66% and a specific surface area of about 5 m2 / g. Each of the porous structures of Examples 4- 7 had the same honeycomb geometry. Each of the porous structures of Examples 4-7 were then loaded directly with the CO2 adsorbent without an interlayer to produce a CO2 capture device. The CO2 adsorbent was PEE

[0188] Each of the CO2 capture devices of Examples 4-7 were then subjected to a CO2 adsorption test using the system 400 shown in FIG. 4 and described in conjunction therewith. For the CO2 adsorption test, cylindrical samples of the porous structure having diameter of 1 inch (2.54 cm) and length of 4 inches (10.16 cm) were coated with the adsorbent. The total volume of each sample was 0.0506 liters. Each CO2 adsorption test included one adsorptiondesorption cycle. During adsorption, an inlet stream comprising air with a concentration of CO2 of about 450 ppm was passed though each sample and the concentration of CO2 in the outlet stream from each sample was measured. The capacity of each of the samples for capturing CO2 was determined from Equation 1 (EQU. 1).In EQU. 1. [CCUJads-iniet is the concentration of the CO2 in the inlet stream during adsorption. [CO2]ads-outiet is the concentration of CO2 in the outlet stream during adsorption, f is the flow rate through the sample, time is the total time that the inlet stream was passed through each sample, and Vsampie was the total volume of each sample.

[0189] For the desorption portion of the cycle, each of the samples was heated to a temperature of 110 °C and purged with nitrogen gas (N2) to release the CO2 from the adsorbent. The desorption capacity of each of the samples for desorbing CO2 from the sample was determined using Equation 2 (EQU. 2).In EQU. 1, [CO2]deS-outiet is the concentration of the CO2 in the outlet stream during desorption, [CO2]des-iniet is the concentration of CO2 in the inlet N2 stream during desorption, f is the flow rate through the sample, time is the total time that the N2 gas was passed through each sample during desorption, and Vsampie was the total volume of each sample.Table 7

[0190] As shown in Table 7, the high surface area porous structures of Examples 6 and 7 having specific surface areas of 13 m2 / g and about 5 m2 / g, respectively, produce a greater CO2 adsorption capacity compared to the porous structures of Examples 4 and 5, which have much lower specific surface areas. Without being bound by any particular theory, it is believed that the high specific surface area of the porous structure may promote the distribution of the PEI,which may increase the accessibility of the CO2 gas to the PEI adsorbents. The greater access of the CO2 to the adsorbent, then, increases the adsorption performance of the PEI adsorbent for adsorbing CO2.

[0191] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.

Claims

ClaimsWhat is claimed is:

1. A porous structure comprising: from 5 wt.% to 95 wt.% hollow glass bodies based on the total weight of the porous structure, the hollow glass bodies comprising a silica-containing glass; and from 5 wt.% to 95 wt.% of a secondary phase based on the total weight of the porous structure, wherein: the hollow glass bodies and the secondary phase are sintered together; at least a portion of the hollow glass bodies are breached; voids defined within the individual breached hollow glass bodies open into one another to form cavities that extend through the porous structure and to outer surfaces thereof; the porous structure has greater than or equal to 50% porosity by volume and a specific surface area greater than or equal to 5 m2 / g.

2. The porous structure of claim 1 , wherein the specific surface area of the porous structure is greater than or equal to 10 m2 / g, or even greater than or equal to 20 m2 / g.

3. The porous structure of claim 1, wherein the porosity of the porous structure is greater than or equal to 55%, or even greater than or equal to 60%.

4. The porous structure of claim 1, wherein the secondary phase comprises: nano-sized inorganic particles having a specific surface area of greater than or equal to 10 m2 / g; nano-sized crystal grains comprising reaction products of a reaction between the silica- containing glass and a coarse inorganic particle having specific surface area less than 10 m2 / g and containing oxides, hydroxides, salts, or combinations thereof of alkali metals or alkaline earth metals; or combinations thereof.

5. The porous structure of claim 4, wherein the secondary phase comprises the nano-sized inorganic particles having high specific surface area of greater than or equal to 10 m2 / g.

6. The porous structure of claim 5, wherein the nano-sized inorganic particles have a specific surface area of greater than or equal to 20 m2 / g, greater than or equal to 50 m2 / g, or even greater than or equal to 100 m2 / g.

7. The porous structure of claim 5, wherein the nano-sized inorganic particles have a median particle size (d50) of from 0.1 nanometers to 100 nanometers.

8. The porous structure of claim 5. wherein the nano-sized inorganic particles comprise gamma alumina, zirconia, zeolite, magnesium oxide, silica, CeO2, TiO2, or combinations of these.

9. The porous structure of claim 5, wherein the nano-sized inorganic particles comprise gamma alumina.

10. The porous structure of claim 4, wherein the secondary’ phase comprises the nano-sized crystal grains comprising the reaction product of the reaction between the silica-containing glass and the coarse inorganic particles.

11. The porous structure of claim 10, wherein the coarse inorganic particles have a specific surface area of less than 10 m2 / g.

12. The porous structure of claim 10, wherein the coarse inorganic particles have an average particle size of from about 100 nanometers to about 100 micrometers.

13. The porous structure of claim 10, wherein the coarse inorganic particles comprise MgO, Mg(OH)2, CaO, Ca(OH)2, Ca3(PO4)2, CaCO3, Li2O, LI2CO3, LI2BO3, Na2O, NaOH, Na2CO3, K2O, KOH, K2CO3, or any combinations thereof.

14. The porous structure of claim 10, wherein the coarse inorganic particles comprise MgO.

15. The porous structure of claim 10, wherein the secondary phase comprises: at least one magnesium-based crystal phase selected from forsterite, clinoenstatite, diopside, or combinations thereof; at least one calcium-based crystal phase selected from wollastonite, pseudo wollastonite, kilchoanite, crostobalite; or combinations thereof.

16. The porous structure of claim 4, wherein the secondary phase comprises nanosized inorganic particles having a specific surface area of greater than or equal to 10 m2 / g and nanosized crystal grains comprising reaction products of a reaction between the silica-containing glass and the coarse inorganic particles having specific surface area less than 10 m2 / g and containing oxides, hydroxides, salts, or combinations thereof of alkali metals or alkaline earth metals.

17. The porous structure of claim 16, wherein the porous structure comprises one or more crystalline phases selected from roedderite, corundum, zirconia, or combinations of these.

18. The porous structure of claim 1, wherein the porous structure comprises a glass phase.

19. The porous structure of claim 1 , wherein the plurality of hollow glass bodies comprise borosilicate glass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate glass, or combinations thereof.

20. The porous structure of claim 1 , wherein the porous structure has a D-factor of greater than or equal to 0.5, wherein: the D-factor is equal to (d5o-dio) / dso; dso refers to a mean pore diameter of the porous structure at which 50% by volume of the open porosity of the porous structure has been intruded by mercury during a porosimetry measurement; and dio is equal to the pore diameter at which 90% by volume of the open porosity of the porous structure has been intruded by mercury during a porosimetry measurement.

21. The porous structure of claim 1, wherein the porous structure has a median pore size of from 1 pm to 50 pm. or from 2 pm to 20 pm.

22. The porous structure of claim 1, wherein the porous structure has a honeycomb shape comprising a plurality of elongate channels extending through at least a portion of the porous structure, wherein the porous structure has a cell density of less than 400 cells per inch and a web thickness between cells of from 2 mils to 8 mils, where the cell density refers to a number of elongate channels per square inch of cross-section of the porous structure.

23. The porous structure of claim 1, wherein the porous structure comprises a size and shape that is within 15% of a size and shape of an extruded green structure prior to firing to convert the extruded green structure into the porous structure.

24. The porous structure of claim 1, further comprising one or more CO2 adsorbents deposited within the cavities of the porous structure.

25. The porous structure of claim 24. wherein the CO2 adsorbents comprise PEI. MEA. DEA, PPI, PPA, NaOH, Na2COs, NaHCCh, KOH, K2CO3, KHCO3, or combinations thereof.

26. The porous structure of claim 24, wherein the CO2 adsorbents are bonded to surfaces of the porous structure defining the cavities.

27. The porous structure of claim 24, wherein the porous structure does not have an interlayer disposed between surfaces of the porous structure and the CO2 adsorbents bonded thereto.

28. A CO2 capture process comprising the porous structure of claim 24, wherein the CO2 capture process comprises an adsorption-desorption unit and the porous structure is integrated into the adsorption-desorption unit.

29. A composition for making a ceramic honeycomb, the composition comprising: a plurality of hollow glass bodies comprising a silica-containing glass; a secondary phase precursor comprising: nanosized inorganic particles having a specific surface area of greater than or equal to 10 m2 / g; coarse inorganic particles having specific surface area less than 10 m2 / g and comprising oxides, hydroxides, salts, or combinations thereof of alkali metals or alkaline earth metals; or combinations thereof; a liquid vehicle; and an organic system.

30. The composition of claim 29. comprising from 50 vol. % to 95 vol. % of the hollow glass bodies and from 5 vol.% to 50 vol.% of the secondary phase precursor, wherein the volumepercentages are based on the total bulk volume of inorganic solid components of the composition.

31. The composition of claim 29. wherein the silica-containing glass comprises borosilicate glass, soda-lime glass, aluminosilicate glass, alkali aluminosilicate glass, or combinations of these.

32. The composition of claim 29. wherein the secondary phase precursor comprises the nano-sized inorganic particles.

33. The composition of claim 32, wherein the nanosized inorganic particles have a specific surface area of greater than or equal to 10 m2 / g.

34. The composition of claim 32, wherein the nanosized inorganic particles comprise gamma-alumina, zirconia, zeolite, magnesium oxide, silica, CeCh. TiCh, or combinations thereof.

35. The composition of claim 29, wherein the secondary phase precursor comprises the coarse inorganic particles comprising the oxides, hydroxides, salts, or combinations thereof of the alkali metals or alkaline earth metals.

36. The composition of claim 35, wherein the coarse inorganic particles comprise MgO, Mg(OH)2, CaO, Ca(OH)2, Ca3(PO4)2, CaCCh. Li2O, Li2CO3, L13BO3, Na2O, NaOH, Na2CO3, K2O, KOH, K2CO3, or combinations thereof.

37. The composition of claim 29, wherein the organic system comprises one or more of methocel, CMC, lubricants, PVP, PVA, or combinations thereof.

38. The composition of claim 29, wherein the liquid vehicle is water, one or more alcohols, or combinations thereof.

39. A porous structure prepared from the composition of claim 29.

40. A porous structure prepared by a process comprising: preparing the composition of claim 29; forming a green structure from the composition; andfiring the green structure at a temperature less than or equal to 1000 °C, or even less than or equal to 900 °C; wherein the porous structure has a porosity of greater than or equal to 50%, and a specific surface area of greater than or equal to 5 m2 / g.

41. The porous structure of claim 40, wherein the porous structure has a size and shape that is within 15%, or even within 1% of a size and shape of the green structure before firing.

42. The porous structure of claim 40, wherein the secondary phase precursor comprises the nano-sized inorganic particles, and firing the green structure bonds the hollow glass micropheres and the nano-sized inorganic particles together and breaches at least a portion of the hollow glass bodies to form the porous structure having the porosity greater than or equal to 50% and the specific surface area of greater than or equal to 5 m2 / g.

43. The porous structure of claim 40, wherein the secondary phase precursor comprises the coarse inorganic particles comprising the oxides, hydroxides, salts, or combinations thereof of the alkali metals or alkaline earth metals, and firing the green structure causes a reaction between the silica-containing glass of the hollow glass bodies to produce nano-sized crystal grains and breaches at least a portion of the hollow glass bodies to form the porous structure having a porosity of greater than or 50% and the specific surface area of greater than or equal to 5 m2 / g.

44. The porous structure of claim 40, wherein firing the green structure comprises: ramping the green structure to the peak firing temperature of less than or equal to 1000°C; and holding the green structure at the peak firing temperature for a period of from 1 hour to 10 hours.

45. The porous structure of claim 40, wherein the porous structure further comprises a CO2 adsorbent bonded to surfaces of cavities of the porous structure, and the process further comprises bonding the CO2 adsorbent to the porous structure.

46. The porous structure of claim 40. wherein bonding the adsorbent to the porous structure does not include applying an interlayer between the surfaces of the porous structure and the CO2 adsorbent.

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