Methods of making an electrically conductive aluminum - containing substrate

Abstract

A method of forming an electrically conductive substrate. The method includes heating a green body by exposing the green body to a heating cycle. The green body includes 30 to 90 % by weight aluminum particles, 10 to 70 % by weight pore former particles, and 2 to 20 % binder by weight in superaddition to the total sum of the aluminum and the pore former particles. Heating the green body includes exposing the green body to the heating cycle for a temperature and a period of time sufficient to sinter the aluminum particles together and form pores from the pore former particles. A metal substrate, an apparatus for gas separation, and a method of carbon dioxide capture are also disclosed.

Description

METHODS OF MAKING AN ELECTRICALLY CONDUCTIVE ALUMINUM - CONTAINING SUBSTRATECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63 / 604,659 filed on November 30, 2023, and U.S. Provisional Application Serial No. 63,604,645 filed on November 30, 2023, the content of which is relied upon and incorporated herein by reference in their entireties.TECHNICAL FIELD

[0002] Embodiments of the present disclosure generally relate to methods of making electrically conductive aluminum-containing substrates and their use such as for removing carbon dioxide from a gas mixture, such as with temperature swing adsorption.BACKGROUND

[0003] Carbon dioxide (CO2) capture and removal by adsorption processes is one of the technological solutions to address the current global climate challenge. Arrangement of a sorbent on a contactor, such as a honeycomb substrate, can be useful in carbon dioxide capture or other gas separation activities.SUMMARY

[0004] In one or more aspects, methods of making an electrically conductive aluminum- containing substrate are disclosed herein.

[0005] In one or more aspects, apparatuses and are methods are disclosed herein for removing, or separating, a selected target gas, such as carbon dioxide gas (“gaseous carbon dioxide”, or “gaseous CO2”, or “CO2”) from a gas or gas mixture or gas volume or gas stream which is to be subjected to the target gas removal, or gas separation, process, herein referred to as “subject gas”, with an electrically conductive aluminum-containing substrate, and methods of making the substrate. Methane or other gases could also be target gases that are captured orseparated from a subject gas. The subject gas may be ambient air (e.g., as in “direct air capture”) or exhaust or effluent gas (e.g., as in “point source capture”).

[0006] In one or more aspects, apparatuses and methods are disclosed herein of removing (or separating) CO2 from a subject gas. Methods disclosed herein comprise at least one cycle comprising the steps of: adsorbing CO2 gas from the subject gas and holding the adsorbed CO2 gas with a sorbent bed, and heating the sorbent bed with one or more electrodes to release at least some of the adsorbed CO2 gas from the sorbent bed, wherein the heating step occurs after the absorbing step, and wherein the one or more electrodes are in contact with the sorbent bed during the heating step.

[0007] In one or more other aspects, apparatuses and methods are disclosed herein of removing (or separating) CO2 from a subject gas, the method comprising at least one cycle comprising the steps of: adsorbing CO2 gas from the subject gas and holding the adsorbed CO2 gas with a sorbent bed, and heating the sorbent bed with one or more electrodes to release at least some of the adsorbed CO2 gas from the sorbent bed, wherein the heating step occurs after the absorbing step, and wherein essentially no subject gas flows into, or out of, or neither into nor out of, the sorbent bed.

[0008] In one or more other aspects, apparatuses and methods are disclosed herein of removing (or separating) CO2 from a subject gas, the method comprising at least one cycle comprising the steps of: adsorbing CO2 gas from the subject gas and holding the adsorbed CO2 gas with a sorbent bed; and heating the sorbent bed with one or more electrodes to release at least some of the adsorbed CO2 gas from the sorbent bed; wherein the heating step occurs after the absorbing step; and wherein the one or more electrodes are in contact with the sorbent bed during the heating step.

[0009] This aspect may further comprise, after the adsorbing step and before the heating step, a step of evacuating (or removing) at least a portion of any gaseous species (which may include gas phase of any liquid present in the container) which may be present inside the container, which may include inside the adsorbent bed or adsorbent material.

[0010] In this aspect, an additional step of cooling the sorbent material is performed, after the heating step and preferably after the purging step if carried out, wherein the step of cooling comprises cooling the sorbent material with a cooling gas stream which is preferably free or essentially free of any oxygen gas species. In embodiments, the cooling gas stream comprises nitrogen. In embodiments, the cooling gas stream comprises water vapor or steam. Inembodiments, the cooling gas stream comprises water vapor. In embodiments, the cooling gas stream comprises steam. In embodiments, the cooling gas stream comprises nitrogen, water vapor, or steam, or combinations thereof.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGS. 1A-1C schematically illustrate three process steps of a temperature swing adsorption (TSA) system which comprises an electrically conductive substrate as disclosed herein as a sorbent bed; FIG. 1A adsorption, FIG. IB heating, FIG. 1C purging.

[0012] FIG. 2A shows a front view showing an end of a shaped bed having a honeycomb structure.

[0013] FIG. 2B shows a cross sectional view taken generally along line B-B in FIG. 2A, showing honeycomb cell walls and the associated axial channels which allow gas to pass through the honeycomb structure in either direction.

[0014] FIG. 3A schematically illustrates the configuration of a sorption unit during the heating step with electrodes applied to, and in contact with, the inlet and outlet faces of the sorbent bed.

[0015] FIG. 3B schematically illustrates the configuration of a sorption unit during the steps other than the heating step, where the electrodes have been moved away, and are spaced away, from the sorbent bed, in which configuration gas flow may pass into and out of the sorbent bed.

[0016] FIG. 4 schematically illustrates an example of substrate comprising a honeycomb structure, which can be in the state of a green body before sintering or a porous aluminum body after sintering.DETAILED DESCRIPTION

[0017] Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways.

[0018] A more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings, in order to help understand the above recited features of the present disclosure in detail. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0019] Direct air capture (DAC) systems need to be energy efficient in order to capture CO2 which may be present in a large quantity of air at relatively low concentration process large amounts of air to capture. Temperature swing adsorption (TSA) can be implemented in a DAC system. Adsorption is preferably at ambient temperature and desorption is at higher temperature. The electrically conductive substrates disclosed herein which are deployed in a TSA system can be joule heated directly, resulting in less energy cost and shorter desorption time. The aluminum -containing substrates disclosed herein are electrically conductive substrates. Adsorbent material can be added to the substrates to enhance adsorption, and the substrates disclosed herein preferably have high surface area which is suitable for higher adsorbent material loading. Thus, the aluminum -containing substrates disclosed herein are preferably electrically conductive with high surface area.

[0020] Aluminum conducts electricity very well, however in order to joule heat , relatively low conductivity is needed.

[0021] Methods disclosed herein comprise at least one cycle comprising the steps of: adsorbing CO2 gas from the subject gas and holding the adsorbed CO2 gas with a sorbent bed, and heating the sorbent bed with one or more electrodes to release at least some of the adsorbed CO2 gas from the sorbent bed, wherein the heating step occurs after the absorbing step, and wherein the one or more electrodes are in contact with, and in some embodiments may be removably in contact with, the sorbent bed during the heating step.

[0022] In embodiments, at least a portion of the CO2 in the CCh-containingsubject gas is removed from the subject gas and held by the sorbent bed, wherein the sorbent bed is disposed within a sorbent bed volume defined by a housing (or container) in which the sorbent bed resides, and the heating step comprises heating the sorbent bed to desorb (or release) at least a portion of the CO2 from the sorbent bed (“desorbed CO2”), wherein essentially no gas escapes from the sorbent bed volume, wherein the heating comprises applying an electric potential to the sorbent bed, and then the desorbed CO2 is purged from the sorbent bed volume.

[0023] In embodiments, the purging comprises introducing a fluid medium into the sorbent bed volume to create a desorb fluid comprising the desorbed CO2. In some embodiments, the fluid medium comprises water vapor or steam or both. In some embodiments, CO2 is separated from the desorb fluid via condensation, for example of the water vapor, or the steam, or both.

[0024] In embodiments, the applying the electric potential comprises contacting the sorbent bed with one or more electrodes. In some embodiments, at least one of the one or more electrodes comprises an electrically conductive contact element for contacting the sorbent bed; in some of these embodiments, the electrically conductive contact element comprises graphite, wire mesh, or combinations thereof; in some embodiments, the electrically conductive contact element is connected to one pole of an electric power supply; in some of these embodiments, the electrode further comprises an support element for supporting the electrically conductive contact element; in some of these embodiments, the support element is electrically insulating; in some of these embodiments, the electrode further comprises an electrically insulating of element disposed between the support element and the electrically conductive contact element.

[0025] In some embodiments, none of the one or more electrodes is disposed inside the sorbent bed.

[0026] Thus, in various aspects disclosed herein are processes, or methods, and apparatuses to remove or separate carbon dioxide from a subject gas which contains CO2 using a temperature swing process (TSA), in which a temperature increase is achieved by electrically heating a sorbent material. The subject gas can be ambient air or another CO2 containing gas or gas mixture. A subject gas with CO2 concentrations of 5% by volume or less may be particularly suitable for the temperature swing process. Thus, electric power or electric current may be intermittently applied to the sorbent bed, during a heating phase of the desorption step, and optionally at other times. The process disclosed herein comprises the steps of: (A) adsorption of CO2 from the subject gas in the adsorbent bed (or sorbent bed) ; (H) heating of the sorbent using an electric potential applied to the sorbent bed, preferably without any gas flow out of the sorbent bed during heating, and in this step electrodes are applied and connected to the sorbent bed, such the inlet face, the outlet face, or both the inlet face and the outlet face; (P) purging of the bed and desorbed CO2 present in the gas phase (such as by using a fluid medium, and preferably creating a fluid flow with high CO2 concentration, for example, which can be further purified in a downstream operation, for example). These steps may constitute a cycle and the steps may be repeated for a plurality of cycles.

[0027] In one aspect the fluid medium for the purge in the purging step can be, for example, water vapor, or steam, which can allow for a relatively simple downstream separation via condensation, leaving a more highly concentrated CO2 product outcome of the process.

[0028] FIGS. 1A-1C schematically illustrate the above three main process steps (FIG. 1A adsorption, FIG. IB heating, FIG. 1C purging) with an apparatus (or sorbent bed unit) 100 that comprises a sorbent bed 20 disposed in a housing or container 30, wherein electrodes 50 come into contact with the sorbent bed during the heating step, and out of contact with the sorbent bed 20 during the adsorption step and the purge step as illustrated in FIGS. 1A-1C. A CO2 — containing gas or gas stream 10 enters the sorbent bed unit 100 comprised of a sorbent bed 20 and housing (or container or column vessel) 30. A CO2 leaner gas stream 40 can exit the sorbent bed unit 100 during the adsorption step. During the heating step, one or more electrodes 50 are in contact with the sorbent bed 20, and preferably electrodes 50 seal in the sorbent bed 20 such that no gas flow, or essentially no gas flow, exits the sorbent bed volume 25 (an example of which is schematically shown by dashed line in FIG. 1A for illustration purposes) in which the sorbent bed 20 is disposed, and in various embodiments no gas flow, or essentially no gas flow, exits the housing 30 either. The sorbent bed volume 25 may be larger than the sorbent bed 20 itself, thereby providing an additional gas situated outside the dimensions of the sorbent bed itself. Electrical supply lines 60 deliver electrical current to the electrode(s) from an electrical power source 70 during the heating step. During the purging step, inlet purge gas 80 enters the housing 30 and the sorbent bed 20, preferably in a direction opposite to the direction of the process stream 10 that occurred during the adsorption step. The gas inside the sorbent bed volume 25 is then preferably forced out of the sorbent bed volume, preferably at a location opposite to the inlet purge gas 80, and exits the sorbent bed volume 25 and the housing 30 as an outlet purge gas 90.

[0029] In various aspects, the process may comprise additional steps, and / or the apparatus may comprise additional components.

[0030] As in all aspects disclosed herein, preferably only during the heating step are electrodes applied and contacting and connected to the inlet and / or outlet face of the sorbent bed. These steps may constitute a cycle and the steps may be repeated for a plurality of cycles. An exemplary cooling gas may comprise nitrogen, or low temperature water vapor, or even steam.

[0031] Thus, as illustrated in FIGS. 1A-1C, in various aspects, an electric potential is applied to the sorbent bed 20 only during the process step during which the adsorbent bed 20 iselectrically heated. Preferably, during the heating step, no gas flow is introduced into the sorbent bed volume 25, and more preferably no gas enters or exits the sorbent bed volume 25 during the heating step. Advantageously, the electrode or electrodes 50 may cover the entire inlet area and / or the entire outlet area of the sorbent bed, thus providing good physical and electrical contacts and distribution of the electric current, thereby providing very rapid and uniform heat up, especially when no convective heat losses occur, as well as minimizing the formation of hot spots due to poor electrode contact or non-uniform path of the electric current.

[0032] Exemplary embodiments are described below. The examples provided are not meant to be exhaustive and further variants can be envisioned.

[0033] FIGS. 2A-2B schematically illustrate an absorbent bed, or sorbent bed, having a rectangular shaped bed, although other that geometry is, such as square, round, oval, etc., are possible. FIG. 2A shows a cutaway side view of the flow direction of the gases. FIG. 2B shows a cutaway top view of the sorbent bed. Housing or shell 30 encases the adsorber sorbent bed 20. In various aspects, gas flow may pass through the sorbent bed in either direction.

[0034] FIG. 3 A schematically illustrates the configuration of the sorption unit 100 during the heating step, here illustrating electrodes 50 applied to, and in contact with, the inlet and outlet faces of the sorbent bed 20. Preferably, the electrodes 50 block gas flow at the inlet and outlet faces of the sorbent bed 20. Motion device 150 provides movement of the electrode(s) 50 into and out of contact with the sorbent bed 20. In various aspects, one or more electrodes 50 also provide a pole of the applied electric potential.

[0035] FIG. 3 A shows the electrodes 50 in contact with the sorbent bed 20, at least during the heating step.

[0036] FIG. 3B schematically illustrates the configuration of the sorption unit 100 in an aspect during the steps other than the heating step, where the electrodes 50 have been moved away, and are spaced away, from the sorbent bed 20, in which configuration gas flow may pass into and out of the sorbent bed 20, as the electrodes 50 have been moved out of physical (and electrical) contact with the sorbent bed 20.

[0037] In various aspects electrode 50 may comprise one or more conductive layers 190 comprised of low electric resistance material and preferably having good mechanical flexibility in order to help achieve a good contact with the ends of the walls 117 of the honeycomb structure or other structure of sorbent bed 20. The conductive layer 190 may be comprised of exemplary materials such as graphite, wire mesh such as metal wire mesh, or other flexible orsoft material with low electrical resistance. The one or more electrically conductive layer 190 is connected to electrically conductive element 210, which is connected to one pole of an electric power supply and has low electrical resistance. In embodiments, electrically conductive element or electric conductor 210 is disposed within movement member 220 which provides for the mechanical movement and is connected to a device that enable this movement. Movement member 220 is preferably electrically insulated from the electric conductor 210. Support member 200 optionally provides for the mechanical strength of the electrode plate and has sufficient stiffness to ensure uniform pressure is applied to the adsorbent bed over the entire cross-section. Support member 200 may be mechanically connected to the conductive layer 190, and may be either made from a material with high electrical resistance, serving an electric insulator itself, or as an electrical insulation layer added between conductive layer 190 and support member 200. Support member 200 may also be mechanically connected to movement member 220.

[0038] In aspects disclosed herein, the sorbent bed comprises an electrically conductive substrate, such as an electrically conductive honeycomb body. We have found that by adding a pore former, such as starch, to aluminum powder, then sintering, the sintering advantageously causes the aluminum particles to bond directly to each other and for the sintered body to be electrically conductive and gain mechanical strength while having sufficient porosity from the pore former particles to enable the sintered body to be coated by and / or impregnated with a selected sorbent. In some embodiments, pyrolysis of the pore former (e.g., starch or other carbon-containing material), for example in an inert environment such as nitrogen gas, may result in the formation of carbonaceous char that imparts a high degree of surface area to the substrate. Substrates having high surface area may be particularly advantageous for loading relatively high amounts of certain types of sorbent materials, thereby increasing the carbon capture efficacy of the substrates described herein.

[0039] Methods are disclosed herein for making an electrically conductive aluminum- composite substrate which can be used as a sorbent bed, wherein the sorbent bed comprises an adsorbent material disposed on, or in, or both on and in, the substrate. For example, a suitable sorbent (adsorbent material) for capturing carbon dioxide can comprise a zeolite, activated carbon, a carbonate (such as sodium carbonate), an amine or amine-containing or functionalized material such polyethyleneimine (PEI) or an amine resin, a metal-organicframework (MOF), a covalent-organic framework (COF) or other material selective to the adsorption of carbon dioxide.

[0040] In an aspect, a method of making an electrically conductive substrate, the method comprising: heating a green body by exposing the green body to a heating environment of one or more temperatures, wherein the green body is comprised of 50 to 90 % by weight aluminum, 10 to 50 % by weight pore former, and 2 to 20 % binder by weight in superaddition to the aluminum and pore former, and wherein the green body is exposed to the heating environment for a period of time sufficient to cause 90% or more of the pore former to bum out of the green body as the green body transforms into the substrate.

[0041] In an aspect, the green body contains 2 to 10 % binder by weight in superaddition to the aluminum and pore former; in an aspect, the green body contains 60 to 80 % by weight aluminum.

[0042] In an aspect, the green body contains 20 to 40 % by weight pore former. In an aspect, the pore former is starch, such as pea starch.

[0043] In an aspect, the green body contains 2 to 15 % by weight binder in super addition to the aluminum and pore former. In an aspect, the green body contains 5 to 10 % by weight binder in super addition to the aluminum and pore former.

[0044] In an aspect, the heating environment comprises a temperature -increasing portion. In an aspect, the temperature-increasing portion comprises increasing temperatures in the heating environment up to 600 to 650° C.

[0045] In an aspect, the heating environment comprises a temperature-hold portion which occurs after the temperature -increasing portion and which comprises holding the green body in a heating environment kept in the range of 600 to 650 °C. In an aspect, the heating environment comprises a temperature -hold portion which occurs after the temperatureincreasing portion and which comprises holding the green body in a heating environment kept in the range of 600 to 650 °C for 0.5 to 2 hours.

[0046] In an aspect, the heating environment comprises a temperature-decreasing portion which occurs after the temperature-hold portion.

[0047] In an aspect, the heating environment is provided by an oven or kiln.

[0048] In an aspect, the temperature-decreasing portion of the heating environment occurs while the oven is in an unpowered state.

[0049] In an aspect, the method further comprises, after the heating, allowing the green body to cool in a room temperature environment.

[0050] In an aspect, the substrate contains greater than 80 % aluminum. In an aspect, the substrate contains greater than 80 % aluminum and has a density which is less than 92% of the theoretical density of pure aluminum. In an aspect, the substrate contains greater than 90 % aluminum.

[0051] In an aspect, the green body is monolithic.

[0052] In an aspect, the green body comprises a honeycomb structure comprised of a plurality of intersecting walls. In an aspect, the substrate is porous. In an aspect, the substrate comprises a honeycomb structure comprised of a plurality of intersecting walls. In an aspect, the intersecting walls and the interior portion are porous.

[0053] In an aspect, the substrate is monolithic.

[0054] In an aspect, the green body is exposed to air in the heating environment. In an aspect, the green body is exposed to air in the temperature-increasing portion of the heating environment. In an aspect, the green body is exposed to air in the temperature-hold portion of the heating environment. In an aspect, the green body is exposed to air in the temperaturedecreasing portion of the heating environment.

[0055] In an aspect, the method further comprises, after the heating, allowing the green body to cool in a room temperature environment.

[0056] In an aspect, the green body is exposed to air in the heating environment. In an aspect, the green body is exposed to air in the temperature-increasing portion of the heating environment. In an aspect, the green body is exposed to air in the temperature-hold portion of the heating environment. In an aspect, the green body is exposed to air in the temperaturedecreasing portion of the heating environment.

[0057] In an aspect, a substrate produced by a method disclosed herein contains greater than 50 % aluminum.

[0058] In an aspect, a substrate produced by a method disclosed herein contains greater than 70 % aluminum.

[0059] In an aspect, a substrate produced by a method disclosed herein contains greater than 90 % aluminum.

[0060] In an aspect, a substrate produced by a method disclosed herein contains greater than 80 % aluminum and has a density which is less than 2,483 kg / m3.

[0061] In an aspect, the substrate comprises a plurality of walls wherein the walls have an average porosity of 40 to 70 %; in another aspect, the substrate comprises a plurality of walls wherein the walls have an average porosity of 45 to 65 %; in another aspect, the substrate comprises a plurality of walls wherein the walls have an average porosity of 45 to 60 %.

[0062] In an aspect, the substrate comprises a plurality of walls wherein the walls have an average BET surface area of 10 to 200 m2 / g; in another aspect, the substrate comprises a plurality of walls wherein the walls have an average BET surface area of 15 to 150 m2 / g.

[0063] In an aspect, the substrate comprises carbonaceous char at least some of which is produced by the pore former, e.g., starch, being exposed to a sintering environment. In particular, the pore former may be a starch, flour, polymer, or other material that bums out during the temperatures required for sintering. In embodiments, the pore former is carbon containing material such that a carbonaceous char is left behind when the pore former is heated in an inert (no oxygen) environment, such as in nitrogen gas.

[0064] In an aspect, the green body is extruded; in an aspect, the green body is monolithic.

[0065] FIG. 4 schematically illustrates an example of a body with a honeycomb structure, i.e., a honeycomb body 400, comprising an array of intersecting walls 402 that define channels 404 extending axially through the body 400. As described herein, the body 400 can be formed by extrusion of an extrudable mixture to form a green body, which can be sintered to provide a substrate comprising a honeycomb structure comprised of a matrix of electrically conductive intersecting walls comprised of, or containing, aluminum.EXAMPLES

[0066] Table 1 lists three example compositions A, B, and C, that can be that extruded into green bodies and fired into sintered aluminum bodies are described further herein, each of which Examples A, B, C were comprised of aluminum, pore former (here, pea starch), and a cellulosic binder (such as a methylcellulose derivative, here specifically a hydroxypropyl methylcellulose, or methyl-hydroxy-propyl-cellulose, binder). The amounts of binder are listed in weight % as a superaddition (“wt% SA”) to the aluminum and starch components.Table 1

[0067] The compositions were extruded into honeycomb bodies and fired according to two different firing methodologies described below with respect to Tables 2 and 3, respectively. In the first firing method, green bodies made from compositions A, B, and C were sintered in an inert atmosphere, and in particular a nitrogen atmosphere. The sintering cycle comprised heating each body from room temperature to 640°C at a ramp rate of approximately 300°C / hour, holding for 2 hours at 640°C, then cooling down to room temperature at a ramp rate of approximately -300°C / hour. Accordingly, Table 2 lists the weight and size for Examples Al, Bl, and Cl using compositions A, B, and C, respectively, each as a green body before sintering, as well as the porosity (in %) as measured by mercury porosimetry and the BET surface area after sintering according to this first sintering method.Table 2

[0068] The green bodies of Examples Al, Bl, and Cl were not electrically conductive (i.e. electrically nonconductive), as indicated by the resistance measured by a multimeter across each sample green body exceeding the maximum resistance range of the multimeter. However, after sintering each of the Examples Al, Bl, and Cl were electrically conductive, having the resistance values reported in Table 2. In general, higher porosity in the sintered body corresponded to higher resistance. That is, the sintered body made in accordance with Example Bl had a higher resistance than that from Example Al, and the sintered body made inaccordance with Example C 1 had a higher resistance than that from both of Examples A 1 and Bl.

[0069] As also reported in Table 2, the firing under inert atmosphere (e.g., nitrogen) resulted in an advantageously high surface areas due to the carbonaceous char remaining from the starch after firing. Accordingly, the value of the BET surface area corresponded to the amount of starch in the composition. That is, the BET surface area of the sintered body made in accordance with Example Bl had a higher BET surface area than that from Example Al, and the sintered body made in accordance with Example Cl had a higher BET surface area than that from both of Examples Al and Bl. This level of BET surface area was not observed in bodies sintered in air, e.g., the second firing method discussed further below with respect to Table 3. That is, when firing in air, the starch is completely, or almost completely, burned off in the presence of the oxygen in air, and therefore does not leave behind any high surface area carbonaceous char.

[0070] Table 3 lists the weight and size for Examples A2 and B2 made from compositions A and B, respectively, each as a green body before sintering, as well as the resistance after sintering, according to the second sintering method (firing in air). Since the same type and amount of pore former was used, the porosity of Examples A2 and B2 resembled that of Examples Al and Bl, respectively.Table 3

[0071] In the second firing method, Examples A2 and B2 were sintered in air (as opposed to an inert atmosphere as described with respect to Examples Al, Bl, and Cl). The sintering cycle comprised heating each body from room temperature to 630°C in approximately 11 minutes (without controlling for a specific value for the increasing temperature heating ramp rate), holding for 1 hour at 630°C, then cooling down to room temperature by shutting off power tothe kiln and allowing to cool naturally to room temperature (without controlling for a decreasing temperature cooling ramp rate °C / hour).

[0072] Aluminum powder reacts quickly with oxygen to form alumina on the aluminum particle surfaces. Since the inclusion of alumina interferes with the direct bonding of aluminum particles, a high alumina-containing body would be mechanically weak. Additionally, alumina is not electrically conductive, so a high alumina-containing body would be generally non- conductive (have relatively high resistance). However, due to the extremely fast heating rate used (e.g., over 600°C in less than 15 minutes), even though Examples A2 and B2 were fired in air (and thus exposed the aluminum to oxygen), the resistances of Examples A2 and B2 after sintering were still very low, and consistent with the values from corresponding Examples A 1 and A2 made from the same composition mixtures A and B, respectively, but fired in inert atmosphere.

[0073] In addition, XRD Rietveld analysis was performed on Examples A2 and B2, which confirmed that Examples A2 and B2 both had high aluminum content (i.e., greater than 90 wt%) and low alumina content (i.e., less than 10 wt%). In particular, Example A2 was 100 wt% aluminum (i.e., essentially 0 wt% alumina), while Example B2 was 94 wt% aluminum and 6 wt% alumina.

[0074] Reference throughout this specification to "one embodiment," "certain embodiments," "one or more embodiments" or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as "in one or more embodiments," "in certain embodiments," "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0075] Although the disclosure herein has been described with reference to particular embodiments, those skilled in the art will understand that the embodiments described are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present disclosure without departing from the spirit and scope ofthe disclosure. Thus, the present disclosure can include modifications and variations that are within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method of forming an electrically conductive substrate, the method comprising: heating a green body by exposing the green body to a heating cycle of one or more temperatures, wherein the green body is comprised of 30 to 90 % by weight aluminum particles, 10 to 70 % by weight pore former particles, such that a total sum of the aluminum and pore former is 100 % by weight, and 2 to 20 % binder by weight in superaddition to the total sum of the aluminum and the pore former particles, and wherein heating the green body comprises exposing the green body to the heating cycle for a temperature and a period of time sufficient to sinter the aluminum particles together and form pores from the pore former particles.

2. The method of claim 1, wherein the green body contains 30 to 90 % by weight aluminum particles.

3. The method of any one of claims 1-2, wherein the green body contains 20 to 60 % by weight pore former particles.

4. The method of any one of claims 1-3, wherein the pore former particles comprise a starch.

5. The method of any one of claims 1-4, wherein the green body contains 2 to 15 % by weight binder in super addition to the aluminum particles and pore former particles.

6. The method of any one of claims 1-5, wherein the green body contains 5 to 10 % by weight binder in super addition to the aluminum particles and pore former particles.

7. The method of any one of claims 1-6, wherein the heating cycle comprises a temperatureincreasing portion.

8. The method of any one of claims 1-7, wherein the temperature-increasing portion comprises increasing temperatures in the heating environment up to 600°C to 650°C.

9. The method of any one of claims 1-8, wherein the temperature-increasing portion comprises increasing temperatures at a rate of at least 250 to 350°C per hour.

10. The method of any one of claims 1-9, wherein the heating is performed in air and the temperature-increasing portion is less than an hour in duration.

11. The method of any one of claims 1-10, wherein the heating is performed in air and the temperature-increasing portion is less than 30 minutes in duration.

12. The method of any one of claims 1-11, wherein the heating is performed in air and the temperature-increasing portion is less than 15 minutes in duration.

13. The method of any one of claims 1-12, wherein the heating cycle comprises a temperaturehold portion which occurs after the temperature-increasing portion and which comprises holding the temperature in the range of 600 to 650°C.

14. The method of any one of claims 1-13, wherein the heating cycle comprises a temperaturehold portion which occurs after the temperature-increasing portion and which comprises holding the temperature in the range of 600 to 650°C for 0.5 to 4 hours.

15. The method of any one of claims 1-14, wherein the heating cycle comprises a temperaturedecreasing portion which occurs after the temperature -hold portion.

16. The method of any of claims 1-15, wherein the method further comprises, after the heating, allowing the green body to cool to room temperature.

17. The method of any of claims 1-16, wherein the substrate contains greater than 80 wt% aluminum and has a density which is less than 2,483 kg / m3.

18. The method of any one of claims 1-17, wherein the substrate contains greater than 90 wt% aluminum.

19. The method of any one of claims 1-18, wherein the substrate contains less than 10 wt% alumina.

20. The method of any one of claims 1-19, wherein the substrate contains less than 7 wt% alumina.

21. The method of any one of claims 1-20, wherein the substrate comprises a plurality of walls wherein the walls have an average porosity of 40 to 70 %.

22. The method of any one of claims 1-21, wherein the substrate comprises a plurality of walls wherein the walls have an average porosity of 45 to 65 %.

23. The method of any one of claims 1-22, wherein the substrate comprises a plurality of walls wherein the walls have an average porosity of 45 to 60 %.

24. The method of any one of claims 1-23, wherein the heating is performed in an inert environment and the pore former leaves in carbonaceous char in the substrate.

25. The method of claim 24, wherein the substrate comprises a plurality of walls wherein the walls have an average BET surface area of 20 to 200 m2 / g.

26. The method of claim 24, wherein the substrate comprises a plurality of walls wherein the walls have an average BET surface area of 50 to 200 m2 / g.

27. The method of claim 24, wherein the substrate comprises a plurality of walls wherein the walls have an average BET surface area of 100 to 200 m2 / g.

28. The method of claim 1 wherein the green body comprises a honeycomb structure comprised of a plurality of intersecting walls.

29. A metal substrate comprising a honeycomb structure of a plurality of intersecting walls defining a plurality of parallel channels extending axially through the substrate, wherein the intersecting walls are electrically conductive porous walls which contain greater than 80 % aluminum and have an average porosity of 40 to 70 %.

30. The metal substrate of claim 29, wherein the walls have an average porosity of 40 to 65 %.

31. The metal substrate of claim 29, wherein the walls have an average porosity of 45 to 65 %.

32. The metal substrate of claim 29, wherein the walls have an average porosity of 45 to 60 %.

33. The metal substrate of claim 29, wherein the walls have an average BET surface area of 20 to 200 m2 / g.

34. The metal substrate of claim 29, wherein the walls have an average BET surface area of 50 to 200 m2 / g.

35. The metal substrate of claim 29, wherein the walls have an average BET surface area of 100 to 200 m2 / g.

36. The metal substrate of claim 29, wherein the substrate contains greater than 90 % aluminum.

37. The metal substrate of claim 29, wherein the substrate contains less than 10% alumina.

38. The metal substrate of claim 29, wherein the substrate contains less than 7% alumina.

39. The metal substrate of any one of claims 29-38 wherein the substrate is monolithic.

40. The metal substrate of any one of claims 29-39, further comprising carbonaceous char.

41. The metal substrate of claim 40, wherein the BET surface area of the substrate is at least 20 m2 / g.

42. The metal substrate of claim 40, wherein the BET surface area of the substrate is at least 50 m2 / g.

43. The metal substrate of claim 40, wherein the BET surface area of the substrate is at least 100 m2 / g.

44. An apparatus for removing separating a target gas from a subject gas, the apparatus comprising: a housing comprising an interior cavity; a sorbent bed disposed within and occupying a sorbent bed volume within the interior cavity, wherein the sorbent bed comprises a sorbent selective to the target gas and an electrically conductive porous aluminum substrate having a porosity of at least 40%, and at least one electrode configured to contact the sorbent bed.

45. The apparatus of claim 44, wherein a first electrode is configured to contact a first end of the sorbent bed and a second electrode is configured to contact a second end of the sorbent bed.

46. The apparatus of any one of claims 44-45, wherein the substrate comprises a honeycomb structure comprised of a plurality of walls forming a plurality of channels extending axially through the substrate.

47. A method of removing CO2 from a subject gas, the method comprising at least one cycle comprising the steps of: adsorbing CO2 gas from the subject gas and holding the adsorbed CO2 gas with a sorbent bed; and heating the sorbent bed with one or more electrodes to release at least some of the adsorbed CO2 gas from the sorbent bed; wherein the sorbent bed comprises an electrically conductive porous aluminum substrate having a porosity of at least 40 % and a sorbent material;wherein the heating step occurs after the absorbing step; and wherein the one or more electrodes are in contact with the sorbent bed during the heating step.

48. The method of claim 47 wherein the one or more electrodes are in contact with the sorbent bed only during the heating step.

49. The method of claim 47 wherein the subject gas flows into the sorbent bed during the absorption step.

50. The method of claim 47 wherein the sorbent bed volume is gas purged during a purging step after the heating step.

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