Patent Application
20240335784
Carbon dioxide (CO2) is one of the main greenhouse gases that traps heat in the atmosphere. CO2 is emitted through human related activities such as transportation, electric power, industry, and agriculture. Some of the larger sources of CO2 emissions are the result of burning fossil fuels, solid waste, and trees as well as through the manufacture of cement and other materials. One way to decrease the amount of CO2 in the atmosphere is to capture CO2 using materials having an affinity for CO2. There is a need for materials that can effectively capture CO2.
The present disclosure provides for sorbents, contactors, methods of using sorbents or contactors to capture CO2, and systems and devices using the sorbents or contactors to capture CO2.
In an aspect, the present disclosure provides for a sorbent comprising: a CO2-philic phase and a support, wherein the CO2-philic phase includes a first type of CO2 binding molecule and a second type of CO2 binding molecule, wherein the first type of CO2 binding molecule and the second type of CO2 binding molecule are different.
In an aspect, the present disclosure provides for a sorbent comprising: a CO2-philic phase and a support, wherein the CO2-philic phase includes a first type of CO2 binding molecule and a second type of CO2 binding molecule, wherein the first type of CO2 binding molecule is polypropylenimine, and the second type of CO2 binding molecule is polyethylenimine.
In an aspect, the present disclosure provides for a contactor, comprising a structure and the sorbent as described above and herein.
In an aspect, the present disclosure provides for a system for capturing CO2 from a gas, optionally the gas is ambient air, comprising: a first device configured to introduce the gas to the sorbent or contactor as described above and herein to bind CO2 to the sorbent; a second device configured to heat the sorbent containing bound CO2 to at least a first temperature to release the CO2, wherein after being heated the sorbent is regenerated so it absorbs CO2 from the gas; and a third device configured to collect the released CO2.
In an aspect, the present disclosure provides for a method of capturing CO2 from gas optionally the gas is ambient air comprising: introducing the ambient air to the sorbent as described above and herein to bind CO2 to the sorbent; heating the sorbent to at least a first temperature to controllably release the CO2; and collecting the CO2 in a CO2 collection device.
In an aspect, the present disclosure provides for a system for implementing the methods as provided above and herein.
Further aspects of the present disclosure will be more readily appreciated upon review of the detailed description of its various embodiments, described below, when taken in conjunction with the accompanying drawings.
Embodiments of the present disclosure provide for sorbents, contactors, methods of using sorbents or contactors to capture CO2, and systems and devices using the sorbents or contactors to capture CO2. The methods, systems, contactors, and sorbents of the present disclosure can be advantageous over current technologies since they are relatively more robust and reduce the cost of capturing CO2, in particular from ambient air. In an aspect, the present disclosure provides for sorbents having an improved CO2-philic phase that has a greater resistance to oxidation and a reduced hydrophilicity.
Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, and as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described.
As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order that is logically possible.
Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of chemistry, materials science, mechanical engineering, and the like, which are within the skill of the art.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to perform the methods and use the probes disclosed and claimed herein. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by volume, temperature is in ° C., and pressure is at or near atmospheric. Standard temperature and pressure are defined as 20° C. and 1 atmosphere.
Before the embodiments of the present disclosure are described in detail, it is to be understood that, unless otherwise indicated, the present disclosure is not limited to particular materials, reagents, reaction materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequences where this is logically possible.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a compound” includes a plurality of compounds. In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings unless a contrary intention is apparent.
The present disclosure provides for sorbents and contactors, methods of using sorbents and contactors to capture CO2, structures including the sorbent, and systems and devices using sorbents to capture CO2. The present disclosure is directed to multiple types of sorbents and structures that will be described below and herein.
In an aspect, the present disclosure provides for sorbents that include a CO2-philic phase and a support. In one aspect, the CO2-philic phase includes a first type of CO2 binding molecule and a second type of CO2 binding molecule. The first type of CO2 binding molecule and the second type of CO2 binding molecule are different molecules (e.g., the first type of CO2 binding molecule can be polypropylenimine and the second type of CO2 binding molecule can be polyethylenimine). The CO2-philic phase can be a homogeneous mixture or a heterogeneous mixture. The CO2 binding molecules contain CO2 binding moieties. The ratio of the amount of the first type of CO2 binding molecules to the second type of CO2 binding molecules can be about 0.0001 to 1 mole of the first type of CO2 binding molecules to mole of the second type of CO2 binding molecules or about 0.01 to 0.5 mole of the first type of CO2 binding molecules to mole of the second type of CO2 binding molecules or about 0.1 to 1 mole of the first type of CO2 binding molecules to mole of the second type of CO2 binding molecules or about 0.1 to 0.5 mole of the first type of CO2 binding molecules to mole of the second type of CO2 binding molecules. When the two types of CO2 binding molecules are combined, an improved CO2-philic phase is created. In an aspect, when the improved CO2-philic phase is incorporated into the pores of a porous support material, for example, an effective CO2 sorbent is formed. Further, the sorbents created with the improved CO2-philic phase lose less of the capacity to capture CO2 following oxidative exposures compared to sorbents created without the improvement to the CO2-philic phase, thereby providing them with longer commercial lifetime. Additionally, the sorbents created with the improved CO2-philic phase are more hydrophilic and can thereby improve performance of the sorbent in a CO2 adsorption process compared to sorbents without the improvement.
Although not intending to be bound by theory, the combination of the two types of CO2 binding molecules allows for the ability to tune the properties of the CO2-philic phase. For example, a CO2 binding molecule that has a greater resistance to oxidative degradation, or a CO2 binding molecule that increases hydrophilicity, or a CO2 binding molecule that has a greater resistance to oxidative degradation and an increased hydrophilcity can be mixed with a CO2 binding molecule that has a high CO2 adsorption capacity, with the aim of imparting the beneficial properties of both CO2 binding molecules on the CO2-philic phase to create an overall improved CO2-philic phase. The amount, type, and mixture quantity of the CO2 binding molecules can be tuned and changed to achieve the desired properties of the CO2-philic phase. One advantage with a mixture of two types of CO2 binding molecules can be realized when the CO2 adsorption capacity is retained, while improved properties with respect to oxidative stability or hydrophilicity are imparted.
A structured support, also referred to as a formed support or as a structure, refers to a support that has been formed into a structure where the structure is, at standard conditions, a solid body. Supports can also be unstructured, at standard conditions having a powdery consistency. When a support is referred to without mention to a structure, forming, or being formed or structured, it can refer to supports that are either structured or unstructured.
Structured supports can take the form of a homogeneous solid body (i.e., comprised predominantly of support but also containing components that allow it to remain a stable body at standard conditions) or as a coating on a substrate, whereby the substrate has a different composition than the coating and provides the mechanical stability to the coating.
It can be useful to utilize a structured support with a CO2-philic phase as a contactor in a process for removing CO2 from a gas stream such as ambient air. Contactors provide a geometry to a CO2-philic phase such that considerations such as pressure drop, throughput, and/or mass transfer rates can be optimized.
The first type of CO2 binding molecule and the second type of CO2 binding molecule can be an amine or an amine polymer. The amine or amine polymer can contain primary amines, secondary amines, tertiary amines, or a mixture of any combination of primary, secondary, and tertiary amines. The amine polymer can be branched, hyperbranched, dendritic, or linear. The CO2 binding moieties are the amine moieties on the amine molecule or polymer. The amine moieties can interact with CO2 to form carbamate, carbonate, or bicarbonate species.
Primary amines are defined as having the structure—NH2R1, where R1 is an alkyl group such as CH2 or CH3. Secondary amines are defined as having the structure—NHR1R2, where R1 and R2 are independently selected from an alkyl group such as CH2 or CH3. Tertiary amines are defined as having the structure —NR1R2R3, where R1, R2, and R3 are independently selected from an alkyl group such as CH2 or CH3.
Linear amine polymers can be defined as containing only primary amines, secondary amines, or both primary and secondary amines. The ratio of secondary to primary amines can be about 0.5 to 10,000. In an aspect, the linear amine polymer can have a molecular weight of about 100 to 100,000 g/mol, about 200 to 30,000 g/mol or about 600 to 5,000 g/mol.
Branched amine polymers can be defined as containing any number of primary, secondary, and tertiary amines, which does not overlap linear amine polymers or dendritic amine polymers. The ratio of primary, secondary, and tertiary can be about 10:80:10 to 60:10:30, about 60:30:10 to 30:50:20, or about 45:45:10 to 35:45:20. As one of skill would understand, the structures of branched amine polymers can vary greatly and can be very complex. In an aspect, the branched amine polymer can have a molecular weight of about 100 to 100,000 g/mol, about 200 to 30,000 g/mol or about 600 to 5,000 g/mol.
Dendritic amine polymers can be defined as containing only primary and tertiary amines, where groups of repeat units are arranged in a manner that is necessarily symmetric in at least one plane through the center (core) of the molecule (e.g., at least one plane can include one plane, two planes, or three planes through the center (core) of the molecule), where each polymer branch is terminated by a primary amine, and where each branching point is a tertiary amine. The core or central linkage is the same as the branching amines (e.g., ethylenimine core and ethylenimine branches, propyleneimine core and propyleneimine branches). The ratio of primary to tertiary can be about 1 to 3. In an aspect, the dendritic amine polymer can have a molecular weight of about 100 to 100,000 g/mol, about 200 to 30,000 g/mol or about 280 to 3,000.
Hyperbranched amine polymers can be defined as having chemical structure resembling dendritic amine polymer, but containing defects in the form of secondary amines (e.g., linear subsections as would exist in a branched polymer), in such a way that provides a random chemical structure instead of a symmetric chemical structure. The hyperbranched amine polymers do not overlap branched amine polymers or dendritic polymers. In a hyperbranched chemical structure, the ratio of primary to secondary to tertiary can be about 65:5:30 to 30:10:60. In an aspect, the hyperbranched amine polymer can have a molecular weight of about 100 to 100,000 g/mol, about 200 to 30,000 g/mol or about 600 to 10,000 g/mol.
In an aspect, linear, hyperbranched and branched amine polymers have secondary amines and dendritic amines do not, which may be advantageous since secondary amines bond strongly to CO2.
In an aspect, the amine polymer can be polyethylenimine or polypropylenimine, where each can be branched, hyperbranched, dendritic, or linear. In an aspect, the first type of CO2 binding molecules and the second type of CO2 can each be linear amine polymers. In an aspect, the first type of CO2 binding molecules and the second type of CO2 can each be branched amine polymers. In an aspect, the first type of CO2 binding molecules and the second type of CO2 can each be hyperbranched amine polymers. In an aspect, the first type of CO2 binding molecules and the second type of CO2 can each be dendritic amine polymers. In an aspect, the first type of CO2 binding molecules can be a linear amine polymer and the second type of CO2 can a branched, hyperbranched, or dendritic amine polymer. In an aspect, the first type of CO2 binding molecules can be a branched amine polymer and the second type of CO2 can a linear, hyperbranched, or dendritic amine polymer. In an aspect, the first type of CO2 binding molecules can be a hyperbranched amine polymer and the second type of CO2 can a linear, branched, or dendritic amine polymer. In an aspect, the first type of CO2 binding molecules can be a dendritic amine polymer and the second type of CO2 can a linear, branched, or hyperbranched amine polymer.
In an aspect, the first type of CO2 binding molecules is polypropylenimine and the second type of CO2 binding molecules is polyethylenimine, where each can independently be branched, hyperbranched, dendritic, or linear.
Although not intending to be bound by theory, the combination of the two types of CO2 binding molecules allows for the ability to tune the properties of the CO2-philic phase. For example, polypropylenimine has been shown to demonstrate greater resistance to oxidative degradation as compared to polyethylenimine. Additionally, the hydrophilicity of the amine polymers is varied. The amount, type, and mixture quantity of the CO2 binding molecules can be tuned and changed to achieve the desired properties of the CO2-philic phase.
In an embodiment, the size (e.g., length, molecular weight), amount (e.g., number of distinct amine polymers), and/or type of amine polymer, can be selected based on the desired characteristics of the porous structure (e.g., CO2 absorption, regenerative properties, oxidative stability, loading, and the like).
In an aspect, it is advantageous to improve the stability of the CO2-philic phase to process conditions relevant to use of the sorbent in a CO2 separation process, particularly during sorbent regeneration (process cycles that raise the temperature of the sorbent to remove bound CO2). It is also advantageous to improve the stability of the CO2-philic phase to conditions relevant to storage of the sorbents when they are not being utilized in a process or plant. Sorbents that have a CO2-philic phase with improved stability with respect to process conditions including sorbent regeneration, storage, or both process conditions including sorbent regeneration and storage are valuable.
Evaluating the oxidative stability of materials in environments that contain oxygen and CO2 is useful due to the fact that during regeneration processes, desorbed CO2 is present at different concentrations in addition to oxygen at elevated temperatures, and can impact the stability of the material. Separately, evaluating the oxidative stability of materials with oxygen only (air) is a useful way to evaluate the shelf life of a material when it is stored at ambient conditions.
As described above, the CO2-philic phase can be homogeneous or heterogeneous. When the CO2-philic phase is heterogeneous, the first type of the CO2 binding molecules and the second type of CO2 binding molecules can be present in a variety of ways. For example, the first and second type of the CO2 binding molecules can be mixed and then applied or incorporated with the structure. In another example, the first and second type of the CO2 binding molecules can be applied or incorporated separately but once applied or incorporated, the first and second type of the CO2 binding molecules form the CO2-philic phase. In an aspect, the first and second type of the CO2 binding molecules can be applied or incorporated separately to form a layer of the CO2-philic phase on a support, such as on the surface of pores of the support. In another aspect, the first type of the CO2 binding molecules can be applied to form a layer on a support (e.g., such as on the surface of pores of the support), and the second type of the CO2 binding molecules can be applied or incorporated separately onto the layer on the support (e.g., such as on the surface of pores of the support). In another aspect, independent of or used in combination with other aspects such as those described above, the first and second type of the CO2 binding molecules can be used to form a part of or all of the support, where the CO2-philic phase functions as described herein. Various combinations are contemplated and are part of the present disclosure. Additional ways in which to apply, use, or incorporate the CO2-philic phase homogeneously and/or heterogeneously are described herein and below.
As described herein, the sorbent includes the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) and the support. The support includes a surface (e.g., a surface that can be exposed to a gas including CO2 during regular use and/or that can interact with the CO2-philic phase). The surface can be the surface of pores and/or other surfaces that the CO2-philic phase contacts or interacts with.
In an aspect, the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) can be disposed on or within a support to form a sorbent. The CO2-philic phase can be disposed on the surface of the support, and/or within pores of the support, and/or on exterior surface of a support or any combination thereof. In an aspect, the CO2-philic phase can be a coating on the surface of the porous material, a monolayer on the surface of the porous material, a self-assembled monolayer on the surface of the porous material, a bulk phase within the pores of the porous material, a coating on the exterior surface of the porous material, and the like.
In an aspect, the support can be made of one or more types of materials such as ceramic, metal, metal oxide, plastic, cellulose, carbon, a zeolite, a metal organic framework (MOF), a porous organic framework (POF), a covenant organic framework (COF), a polymer of intrinsic microporosity (PIM), a polymer, a fibrous cellulose, fiberglass, boron-nitride fiber, and the like. In another aspect, the support can be made of materials that also include the CO2-philic phase.
The metal oxide support can be selected from cordierite, alumina (e.g., γ-alumina, θ-alumina, δ-alumina), cordierite-α-alumina, silica, aluminosilicates, zirconia, germania, magnesia, titania, hafnia, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicates, zircon, petalite, and combinations thereof. In cases where the oxide contains a formal charge, the charge can be balanced by appropriate counter-ions, such as cations of NR4, Na, K, Ca, Mg, Li, H, Rb, Sr, Ba, Cs or anions including phosphate, phosphite, sulfate, sulfate, nitrate, nitrite, chloride, bromide and the like. The metal oxide can contain dopants such as zirconium, iron, tin, silicon, titanium, magnesium, and combinations thereof. It is known that metal oxides can contain acid, base, and neutral sites on their surfaces and that dopants can alter the amount and strength of acid and base sites on the surfaces.
In an aspect, the polymer support can be a polymer and/or copolymer of polyolefin(s), polyester(s), polyurethane(s), polycarbonate(s), polyetheretherketone(s), polyphenylene oxide(s), polyether sulfone(s), melamine(s), polyamide(s), polyvinylbenzene, polystyrene-divinylbenzene, polyurethane, polyacrylates, polystyrenes, polyacrylonitriles, polyimides, polyfurfural alcohol, phenol furfuryl alcohol, melamine formaldehydes, resorcinol formaldehydes, cresol formaldehyde, phenol formaldehyde, polyvinyl alcohol dialdehyde, polycyanurates, polyacrylamides, various epoxies, agar, and agarose, or combinations thereof.
The support can be porous (e.g., macroporous, mesoporous, microporous, or mixtures thereof (e.g., where a macroporous surface can include mesopores, and/or micropores, within one or more of the macropores, where a mesoporous surface can include micropores, and so on)). In an aspect, the porous structure is mesoporous. The pores can extend through the porous structure or porous layer or only extend to a certain depth. The macropores of the porous structure can have pores having a diameter of about 100 nm to 10,000 nm, a length of about 500 nm to 100,000 nm and a volume of 0.2-1 cc/g. The mesopores of the porous structure can have pores having a diameter of about 5 nm to 100 nm, a length of about 10 nm to 10,000 nm, and a volume of 0.1-2 cc/g. The micropores of the porous structure can have pores having a diameter of about 0.5 to 5 nm, a length of about 0.5 nm to 1000 nm and a volume of about 0.1-1 cc/g.
The support can be porous and have a porosity of at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, at least 65%, at least 60%, or about 60 to 90%. In some embodiments, the support can have a surface area of 1 m2/g or more, 10 m2/g or more, 100 m2/g or more, 150 m2/g or more, 200 m2/g or more, or 250 m2/g or more, 500 m2/g or more, 1000 m2/g or more.
In an embodiment, the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) can be physically impregnated in the internal volume pores of the porous structure and not covalently bonded to the internal surface of the pores of the porous structure, can be grafted (e.g., covalently bonded directly or indirectly) to the internal surface of the pores of the porous structure, or a combination thereof. In an embodiment, the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) can be covalently bonded (e.g., directly to the surface or via a linker group) (optionally only one of the first and second type of CO2 binding molecules is covalently bonded and the other is not (e.g., the other is physically impregnated)) to the surface of the material, which may include the internal surface of pores for a porous layer or porous structure. In an aspect, the covalent bonding can be achieved using known techniques in the art for bonding sorbents. In regard to the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) being physically impregnated in the pores of the porous structure and not covalently bonded to the internal surface of the pores of the porous structure (e.g., neither the first or second type of CO2 binding molecules is covalently bonded to the internal surface of the pores), the CO2-philic phase can otherwise be bonded or attached to the surface (e.g., Van der Waals, ionic bonds or hydrogen bonds). In yet another embodiment, the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) is present in a plurality of pores (internal volume) of the porous structure (“porous structure” can include a structure having pores in its surface or a structure having a porous layer or coating on the surface of the structure (where the structure itself may or may not be porous)), where the CO2-philic phase has a loading of about 10% to 75% by weight of the support. In regard to the loading, the loading is determined by thermogravimetric analysis (TGA).
In an embodiment, the support can include a surface layer on the surface of the pores of the support that can bond with the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules). In an aspect, the surface layer can include organically modified moieties (e.g., alkyl groups, amines, thiols, phosphines, and the like) on the surface (e.g., outside and/or inside surfaces of pores) of the material. In an embodiment, the surface layer can include surface alkyl groups, amines, thiols, phosphines, and the like, that the CO2-philic phase can directly covalently bond and/or indirectly covalently bond (e.g., covalently bond to a linker covalently bonded to the material). In an embodiment, the surface layer can include an organic polymer having one or more of the following groups: alkyl groups, amines, thiols, phosphines, and the like. In another embodiment, the structure can be a carbon support, where the carbon support can include one or more of the following groups: alkyl groups, amines, thiols, phosphines, and the like.
In an embodiment, the CO2-philic phase can occupy about 10 to 100% of the mesopore volume of the support or can occupy about 30 to 90% of the mesopore volume of the support or can occupy about 40 to 80% of the mesopore volume of the support or can occupy about 50 to 70% of the mesopore volume of the support.
The process of making a formed support or structure described above and herein can be used to create any of the structures listed in this paragraph and those in the following paragraphs. The sorbent, comprising the CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) and the support, can be formed into or applied to a structure. In an aspect, the CO2-philic phase and the support can form 100% of the structure or less than 100% (e.g., each combination of ranges between about 10%, about 20%, about 30%, about 40%, about 50% and about 60%, about 70%, about 80%, about 90%, about 99% such as about 10-99%, about 10 to 80%, about 10 to 50%, about 50 to 99%, about 50 to 90%, about 50 to 80%), where a sufficient amount of sorbent is on the surface of the structure to absorb the desired amount of CO2. In an aspect, the structure can be a honeycomb, a laminate sheet, a foam, fibers, gyroids, powder trays, pellets, powder, and the like or a combination of two or more of the foregoing.
In an aspect, the structure can be porous and have a porosity of at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, at least 65%, at least 60%, or about 60 to 90%.
In an aspect, the porosity of the structure can be comprised of macropores, mesopores, and/or micropores. In an aspect, the CO2-philic phase is predominantly (e.g., about 40 to 100% or about 50 to 90%, or about 60 to 80%) located within the mesopores of the structure.
In an aspect, the structure can be comprised entirely of sorbent or can contain another substrate material such as ceramic, metal, metal oxide, plastic or another material. The structure can be a porous substrate and can also include a porous coating on some or all parts of the porous substrate, where the CO2-philic phase can be present in the pores of one or both of the porous substrate and the porous coating.
When the structure is comprised entirely of sorbent (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules), it can be formed by extrusion, molding, 3D printing, and the like, for example. The structure can be formed using support material without the CO2-philic phase or using the support with the CO2-philic phase already incorporated. When formed without using the CO2-philic phase, the CO2-philic phase can be incorporated into the structure through an impregnation, grafting, or other functionalization technique.
In a particular aspect, the support material can be applied to a substrate as a porous coating (also referred to as a “washcoat”) on the surface of the substrate. In an embodiment, the porous coating can be a foam such as a polymeric foam (e.g., polyurethane foam, a polypropylene foam, a polyester foam, and the like), a metal foam, or a ceramic foam. The porous coating can include a metal-oxide layer (e.g., such as a foam). The metal-oxide layer can be silica or alumina on the surface of the substrate, for example. The porous coating can be present on the surface of the substrate, within the pores or voids of the substrate, or a combination thereof. The porous coating can be about 50 μm to 1500 μm thick and the pores can be of the dimension described above and herein.
In an aspect, the support material, the substrate, and/or the structure can be made of a ceramic substrate such as cordierite, alumina (e.g., γ-alumina, θ-alumina, δ-alumina), cordierite-α-alumina, silica, aluminosilicates, zirconia, germania, magnesia, titania, hafnia, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicates, zircon, petalite, and combinations thereof. The metal or metal oxide structure can be aluminum, titanium, stainless steel, a Fe—Cr alloy, or a Cr—Al—Fe alloy. In cases where the oxide contains a formal charge, the charge can be balanced by appropriate counter-ions, such as cations of NR4, Na, K, Ca, Mg, Li, H, Rb, Sr, Ba, Cs, or anions including phosphate, phosphite, sulfate, sulfate, nitrate, nitrite, chloride, bromide and the like.
In an aspect, the support material, the substrate, and/or the structure can be made of a plastic substrate that can be made of a polymer and/or copolymer of polyolefin(s), polyester(s), polyurethane(s), polycarbonate(s), polyetheretherketone(s), polyphenylene oxide(s), polyether sulfone(s), melamine(s), polyamide(s), polyvinylbenzene, polystyrene-divinylbenzene, polyurethane, polyacrylates, polystyrenes, polyacrylonitriles, polyimides, polyfurfural alcohol, phenol furfuryl alcohol, melamine formaldehydes, resorcinol formaldehydes, cresol formaldehyde, phenol formaldehyde, polyvinyl alcohol dialdehyde, polycyanurates, polyacrylamides, various epoxies, agar, and agarose, or combinations thereof.
In an embodiment, the structure can be a honeycomb structure such as a honeycomb monolith structure that includes channels. The honeycomb structure can have a regular, corrugated structure. The honeycomb monolith structure can have a length and width on the order of cm to m while the thickness can be on the order of mm to cm or more. In an aspect, the honeycomb monolith structure does not have fibrous dimensions. In other words, the honeycomb structure can be a flow-through substrate comprising open channels defined by walls of the channels. The channels can have about 50 to about 900 cells per square inch. The channels can be polygonal (e.g., square, triangular, hexagonal, octagonal) sinusoidal, circular, or the like, in cross-section. Along the length of the channel, the channel length can have a configuration that is straight, zig-zag, skewed, or herringbone in shape. The length of the channel can be 1 mm to 10s or 100s of cm or more. The channels can have walls that are perforated or louvered. In an aspect, the sorbent can be disposed in the pores of the honeycomb structure and/or in the pores of a porous layer on the surface of the honeycomb structure. The honeycomb structure can have a geometric void fraction, otherwise known as the open face area, of between 0.3 to 0.95 or about 0.5 to 0.9.
In an embodiment, the honeycomb structure can comprise an inlet end, an outlet end, and inner channels extending from the inlet end to the outlet end. In some embodiments, the honeycomb comprises a multiplicity of cells extending from the inlet end to the outlet end, the cells being defined by intersecting cell or channel walls.
In an aspect, the honeycomb structure and/or substrate can be ceramic (e.g., of a type produced by Corning under the trademark Celcor®) that can be used with the sorbent in accordance with the principles of the present disclosure. The sorbent can be coated or otherwise immobilized on the inside of the pores of the ceramic honeycomb structure and/or within a porous layer on the surface of the ceramic honeycomb structure. In an aspect, the porous coating can include a metal-oxide layer such as silica or alumina on the surface of the substrate. In an embodiment, the metal-oxide layer can be mesoporous and macroporous. The honeycomb monolith may have a depth of 3 inches to 10 feet or about 3 and 24 inches.
In an aspect, the structure can be laminate sheets. Laminate sheets are structures containing a one-dimensional wall structure, whereby sheets are stacked upon one and other with space in between each sheet such that gas can flow between the sheets.
In an aspect, the structure can be a foam. Foams are structures with an irregular channel structure surrounded by an irregular solid structure. The solid structure is interconnected such that the foam material is self-standing.
In an aspect, the structure can be a plurality of fibers. Fibers are structures with high aspect ratio, and in gas contacting applications can be arranged in a regular array amongst one another when supported at least on one end of the fiber. The fibers can be solid or hollow.
In an aspect, the structure can be a minimal surface solid. Minimal surface solids are structures often used in packing for distillation and absorption systems to increase contact area with a material and a fluid. Minimal surface area solids are geometries that have zero mean surface area and include shapes such as gyroids. Gyroids can be sinusoidal, for example.
In an aspect, the structure can be a powder tray. Powder trays are structures whereby trays hold loose powder or pellets of the sorbent of the present disclosure to form a structured contactor without the material forming a self-standing structure by itself. Powder trays can be arranged in stacked layers to form sheets thereby forming a structure similar to a laminate. These layers can be created using flexible sheets, stiff sheets, or other flat surface that is mounted on a stiff frame structure. Powders are loose, free flowing solids with small characteristic particle diameter such as to provide a powdery consistency. Pellets are beads, balls, or other compacted structures used to provide structure and surface area to sorbents.
In an aspect, the structure can be sorbent particle volumes. Sorbent particle volumes can be contained by one or more walls such that gas can pass through them while keeping the sorbent contained. Sorbent particle volumes can be arranged relative to other sorbent particle volumes such as to approximate a monolith, fiber, or other structured contactor with a solid body.
In an aspect, the sorbent (e.g., structure) in the form of a contactor is an efficient embodiment for an effective method for capturing CO2 from ambient air or other gas mixtures (e.g., flue gas, exhaust gas, natural gas, or other gasses containing CO2) because a structured contactor, or a contactor, can be engineered to provide high surface area and low pressure drop for the air processing. Contactors can take the forms described of a honeycomb, a laminate sheet, a foam, fibers, minimal surface solids, powder trays, pellets, powder, and the like or a combination of two or more of the foregoing.
Now having described embodiments of the sorbent and structure, details regarding the systems and methods of the present disclosure are provided. The present disclosure provides for methods of capturing CO2 from ambient air or other gas mixtures (e.g., flue gas, exhaust gas, natural gas, or other gasses containing CO2). The method includes introducing the ambient air to the sorbent (e.g., structure), heating the sorbent (e.g., about 10 to 200° C. above the regular sorbent temperature to absorb the CO2) to at least a first temperature to controllably release the CO2; and collecting the CO2 in a CO2 collection device. The temperature increase in the sorbent can be performed by contacting the sorbent with a gas at elevated temperature, contacting the sorbent with a fluid at an elevated temperature, contacting the sorbent with a heat exchanger with hot fluid or gas running through it, by heating the walls of the container, vessel, or other containment device that contains the sorbent, or by contacting the sorbent with steam (e.g., the steam may be at a temperature between 60 to 200° C., and be saturated or superheated). In an aspect, the method can be implemented using the system described below.
The present disclosure provides for systems and devices for capturing CO2 from ambient air or other gas mixtures (e.g., flue gas, exhaust gas, natural gas, or other gasses containing CO2) where removal of CO2 is important. In general, the system includes a first device configured to introduce the ambient air or other gas mixture to the sorbent or contactor, where the sorbent or contactor includes those described herein. The sorbent is exposed to the ambient air or other gas mixture for a period of time (e.g., hours). In a particular aspect, the sorbent is a honeycomb monolith that has an open face area of between 0.3-0.95. The first device is configured to deliver the ambient air, for example, to the honeycomb monolith at a velocity of between 0.25-10 m/s. After the desired amount of time, a second device configured to heat the sorbent containing bound CO2 to at least a first temperature to release the CO2. The second device of the system can operate to desorb CO2 by the sorbent. The second device can include components to support temperature swing, pressure swing, steam swing, concentration swing, combinations thereof, or other dynamic processes to desorb the CO2. In an embodiment, the steam swing process can include exposing the sorbent to steam, where the temperature of the steam is about 60° C. to 150° C. and the pressure of the steam is about 0.2 bara to 5 bara. A third device is configured to collect the released CO2. The system can be operated so that the sorbent absorbs and desorbs the CO2 in an efficient and cost-effective manner.
The present disclosure includes the following aspects. The aspects are not limiting but rather include various features and combinations of features of the present disclosure.
The removal of CO2 from ambient air through engineered chemical processes, otherwise known as Direct Air Capture (DAC), is emerging as an important environment technology for the mitigation of climate change. DAC is a technology that can provide negative emissions, removing CO2 from the atmosphere. However, the current DAC technology is expensive thereby limiting its deployment. Therefore, improvements to DAC technology are needed.
Many DAC technologies rely on solid sorbent materials as a medium to perform the separation of CO2 from the air. These sorbents are generally applied in temperature swing processes, where at low temperature CO2 from the air binds to the sites within them, and then at high temperature the CO2 is released into a concentrated product that can be sequestered or sold as a product. Many DAC sorbents utilize amines to bind CO2 in this manner. Certain amine types can be effective at binding CO2 from low concentrations such as that found in the air (400 ppm).
While some amine types are effective at binding CO2 from ambient air, they slowly oxidize in air from ambient oxygen. This effect is exacerbated in process cycles that raise the temperature of the sorbent to remove bound CO2, thereby creating accelerated oxidative degradation that reduces the lifetime of the CO2 sorbents. Therefore, sorbents with improved oxidative stability that are effective at removing CO2 from ambient air are needed.
Some sorbents used in DAC processes are composite materials, containing a CO2-philic phase (e.g., homogeneous or heterogeneous combination of the first and second type of the CO2 binding molecules) that is distributed in or within a solid material that provides it with surface area. The CO2-philic phase can be grafted to the solid surface, physically impregnated into the pores of the solid material, or physically supported on the surface of the solid material. The CO2-philic phase of these sorbents can be amines or other molecules that can bind CO2. In some cases, the amines can be polymeric amines such as polyethylenimine, polypropylenimine, polyallylamine, polyvinylamine, polybutylamine or others. These polymeric amines can be linear, branched, hyperbranched, dendritic, or take the form some other macromolecule. In other cases, the amines can be small molecules such as TEPA, TPTA or others. In other cases, the amines can be aminosilanes. The solid support material can be a metal oxide, carbon, metal, or other structure that can provide ample surface area for the CO2-philic phase to be deposited to allow for useful CO2 adsorption and desorption capacities and kinetics. In this way, the solid support material is functionalized with the CO2-philic phase to create a composite sorbent.
The sorbents can be formed or incorporated into macrostructures, or contactors, to provide advantages in applications such as DAC. Such structures can be honeycomb monoliths, laminate sheets, pellets, or other structures that can provide a high geometric surface area for air or CO2 containing gasses to efficiently contact the sorbent such that the CO2 can bind to the sorbent.
The sorbents can be utilized in processes to capture CO2 from air or a variety of other gas stream such as flue gas, natural gas and others. These processes are known as “CO2 Capture Processes”. CO2 capture processes can utilize temperature swing, concentration swing, pressure swing, steam stripping or other swing techniques to remove CO2 that has been bound the surface of the sorbent.
There has been relatively little development of improved CO2 sorbents utilizing polyethylenimine, and especially for DAC applications.
Now having described the embodiments of the present disclosure, in general, the following examples describes some additional embodiments of the present disclosure. While embodiments of the present disclosure are described in connection with these examples and the corresponding text and figures, there is no intent to limit embodiments of the present disclosure to these descriptions. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of embodiments of the present disclosure.
Solid sorbents made of small amine molecules and polyamines infused into mesoporous substrates are promising materials for CO2 capture technologies. To date, their preparation is mainly based on wet infusion with focus on increasing amine content by varying the structure of the amine sorbent and designing solid substrates of various pore parameters. Less explored in the field are changes in processing to afford efficient CO2 sorbents. In this study, branched polyethylenimine (bPEI, Mw=800 Da) alone and blends with linear polypropylenimine (LPPI, Mn=6,700 Da) are infused into solid SBA-15 substrates by a method that varies the solution processing called sequential polymer infusion into solid substrates (SPISS). The reference 40% bPEI-SBA-15 samples are split by two methods: split batch in dry suspension (SBD) and split batch in liquid suspension (SBL). Sequentially, alcoholic 10% of bPEI (non-blends) and 10% of LPPI (blends) solutions are introduced to afford the desired products. Under dry conditions, the resulting 50% bPEI-SBA-15 SBD & SBL sorbents display high CO2 capacities up to 3.47 mmol CO2/gsio2 for simulated flue gas (10% CO2) and 2.62 mmol CO2/gsio2 for direct air capture (DAC, 400 ppm CO2). Under humid DAC conditions the CO2 performance is further enhanced with an uptake of 4.62 mmol CO2/gsio2 and amine efficiency of 0.22 mmol CO2/mmol N. Subjected to extended temperature swing adsorption kinetic cycling (20 cycles), the SPISS samples display stable working capacities and retain over 70% (blends) and over 90% (non-blends) of their initial 12 h adsorption performance. LPPI is demonstrated to be an effective water sorption limiting agent using dynamic vapor sorption measurements. Solid state NMR techniques reveal important insights into the dynamics of the amine polymers confined into SBA-15 pores, as impacted by processing conditions. The results indicate that the conformation of the polymers is different depending on the processing method, displaying relatively tight (SBD) and loose (SBL) packing. The simple solution processing approaches presented here show that processing variations may guide the design of solid amine sorbents with desirable properties relevant for integration into CO2 capture technologies.
The continuous economic development associated with growing industrialization and the rise in the global population has driven growth in energy production and concomitant accumulation of carbon dioxide (CO2) in the atmosphere. CO2 is one of the key greenhouse gases linked to climate change,1 where the main sources contributing to the growth of the atmospheric CO2 concentration emissions stem from fossil fuel combustion for energy and from chemical processes.2 The atmospheric CO2 concentration reached a record high concentration value of 415 ppm in July of 20213 and will continue to increase another 10% by 20402 To reduce the most significant negative impacts of anthropogenic CO2 on climate and, at the same time, meet the goals set by the Paris Agreement of limiting global warming to 1.5° C.,4 continued advances and deployments in carbon capture, utilization and sequestration are essential.
Carbon capture and utilization (CCU)5 and carbon capture and storage (CCS)6, 7 are two of the main ways available to limit the impact of CO2 on climate change. CCU technologies have recently attracted interest because the captured CO2 is regarded as a renewable resource.8, 9 Processes focused on conversion of CO2 into sustainable products can potentially complement or supplant the use of conventional petrochemical feedstock.10 Yet large scale implementation of CCU remains highly challenging due to the thermodynamic stability of CO2.11 On the other hand, CCS technologies aim to selectively remove CO2 from various gas streams. These streams include dilute mixtures (5-20% CO2) such as those from coal, or gas-fired power plants as well as large industrial sources.12-16 Conventional, point source capture, in conjunction with a transition to renewable energy as well as deployment of more efficient energy consuming devices all produce a common product referred to as “avoided emissions”. Deployment of these technologies help society slow the pace at which we are making climate change worse.
However, in parallel, we need to try to reverse climate change by removing CO2 from the atmosphere. Processes focused on CO2 removal, also referred to as negative emission technologies (NETs), produce a complementary product called “avoided emissions,” as mentioned in the preceding paragraph. Direct air capture (DAC) is an emerging technology that is focused on extracting CO2 from the ambient air (ultra-dilute CO2 source).17 DAC is a negative CO2 emissions technologyl18 when it is coupled with carbon sequestration, such as compression of CO2 to the supercritical state and storage in geological formations (e.g. gas and depleted oil reservoirs, etc.).19 The large scale deployment of CCS, either from point sources (avoided emissions) or the atmosphere (negative emissions), has been limited by policymakers who view the costs (primarily associated with capture and compression)20 as too high. Therefore, developing processes that reduce the cost of CO2 capture technologies is an important challenge.21-23
Many approaches have been developed for breakthrough cost reductions and one of the most promising is the use of amine-functionalized solid sorbents for adsorption-based CO2 capture.24-26 As a function of the preparation method, amine-based sorbents were divided into three classes.26 Class I sorbents uses wet infusion of amine molecules or amine polymers to incorporate amine moieties into the pores where some amines physically bind to the solid support.26, 27 The covalent grafting method is usually used for the class II sorbents where typically aminosilane molecules are chemically bound to the support surface.26, 28 Class III sorbents involve covalent grafting of polymeric amines to the support via in situ-polymerization,29 whereas class IV combines the preparation methodologies of the class I and class II sorbents.30, 31 To be cost effective, these sorbents must ideally display key properties: high adsorption capacity, fast kinetics, low energy for regeneration (e.g., Cp, ΔHads, etc.), rapid heat transfer and long lifetime.17, 32
To date, engineering of these materials has mainly exploited a growing knowledge of their structure-property relationships. The design space has employed a variety of solid mesoporous supports. The most well-studied are mesoporous silicas (SBA-15, MCM-41, MCM-48, MCF, etc.),33, 34 metal-organic frameworks (MOFs)35, 36 and γ-alumina.37 The most frequently used amine molecules for infusion into mesoporous substrates (class 1 or 4 sorbents) are small molecules like diethanol amine (DA),28 or tetraethylenepentamine (TEPA)38 as well as low molecular weight polymers or oligomers such as polyallylamine (PAA)39 and branched and linear polyethylenimine (b/LPEI).40, 41 Each year, new amine molecules or oligomers/polymers are introduced, with recent examples being branched and linear polypropylenimine (b/LPPI),42, 43 polyglycidylamine,44 or molecular aryl-alkyl amines45. The most researched amine molecules from the above examples are TEPA35, 46, 47 and PEI.27, 41, 48
To increase the efficacy of the sorbents, many efforts were dedicated to designing porous supports with different channel geometries, pore size or chemical composition.49-56 These design variations typically targeted maximization of the amine loading and or improvement of gas diffusion through the sorbents, with a goal of increasing the CO2 adsorption performance without causing significant mass transfer limitations due to pore clogging. One of the most used solid supports in CO2 adsorption studies is SBA-15. For example, Olea et al. synthesized mesostructured SBA-15 with expanded pores from the most common pore sizes of 6-7 nm to 11-15 nm.50 Their 50% PEI and 50% TEPA-infused SBA-15 sorbents showed improved CO2 adsorption capacity (3.13 and 3.72 mmol CO2/g) and amine efficiencies (0.33 and 0.37 mmol CO2/mmol N) at 45° C., 1 bar and pure CO2. The authors associated the observed enhanced CO2 performance parameters with the high N content of the samples enabled by the available high pore volume of the modified SBA-15 (1.18 cm3/g). Lashaki and Sayari studied the effect of support pore structure and CO2 adsorption properties as well.54 They concluded that large pore size as well as high intrawall pore volume allow for higher surface amine density and improved amine accessibility reflected by the enhanced adsorptive properties.54 A comprehensive list (up to 2017) of PEI-silica-based sorbents is available in the review by Shen et al.41 All these studies utilized traditional methods of wet infusion and/or grafting of the amine molecules into the supports.
Besides infusion into porous solid supports, other approaches have been used to increase the CO2 performance PEI. For example, Rim et al. developed a complex system made of PEI-tethered silica nanoparticles with ionic bonds (called NOHM-I-PEI) that were incorporated as liquid-like droplets into a continuous silicone acrylate phase via shear emulsification (NPEI-SIPs).57 For 49% NOHM-I-PEI loading, the authors reported CO2 adsorption values of 3.1 mmol CO2/g NPEI-SIPs for 15% CO2 and 1.7 mmol CO2/g NPEI-SIPs for 400 ppm CO2 under humid conditions (2.5% H2O).57 In another example, Xu et al. prepared a non-porous hydrogel by crosslinking PEI with triglycidyl trimethylpropane (TTE) called PEI “snow”.58 They used ambient air as a source of CO2 without dehumidification and reported moderate uptakes of 1.19 mmol CO2/g sorbent and 1.29 mmol CO2/g sorbent for 1000 and 2000 mL/min flow rates, respectively.58 Liu et al. combined wet infusion and chemical crosslinking and synthesized a hyper-crosslinked poly (styrene) resin infused with PEI.59 The highest CO2 uptake value was 3.24 mmol/g at 25° C. under 10% CO2 stream.59 Yoo et al. reported a self-supported polymeric adsorbent entirely made of crosslinked branched PEI.60 Crosslinking was achieved by using poly (ethylene glycol) diglycidyl ether via an ice templating approach. The sorbent had high amine efficiency of 0.32 mmol CO2/mmol N and CO2 uptake of 2.81 mmol CO2/gsorbent at 25° C. under 10% CO2 and 1 bar conditions. This performance was further enhanced to 5.5 mmol CO2/gsorbent under humid conditions (65% RH).60 These examples undertook more complex approaches to preparing amine-based sorbents that may challenge the cost and scale up requirements for an efficient CO2 capture process. Therefore, simpler processes would be advantageous. In line with this idea, an underexplored approach in the field of CO2 capture for designing efficient solid amine sorbents is variations in their solution processing that can greatly impact the targeted properties.
This study demonstrates that manipulation of structure-processing-property relationships results in amine-based solid sorbents with enhanced CO2 adsorption performance. bPEI and blends of bPEI/LPPI infused into SBA-15 composites were prepared by wet infusion and by varying the solution processing, a method denoted as sequential polymer infusion into solid substrates (SPISS). bPEI was sequentially introduced into mesoporous SBA-15 via two methods: split batch in a dry suspension (SBD) and split batch in a liquid suspension (SBL). The CO2 uptake of the prepared sorbents was explored under both dry and humid conditions for 10% CO2 (simulated flue gas) as well as 400 ppm CO2 (DAC) conditions. LPPI was blended with bPEI in a low percentage to test whether its hydrophobic character can limit water uptake and impact adsorption performance. The behavior of the SPISS samples under working conditions was evaluated by extended temperature-swing adsorption-desorption kinetic cycling. Solid state NMR techniques revealed interesting insights about the processing impacts on the morphology of the polymers (bPEI and LPPI) under pore confinement. The study presented here represents an example of harnessing simple solution processing approaches that broaden the design space for polymer-based composites with desirable enhanced CO2 capture properties.
After synthesis, the SPISS samples were thermogravimetrically combusted under nitrogen to determine their organic content that was evaluated from the 150° C. and 700° C. temperature range (
Cryogenic N2 physisorption was used to evaluate the surface specific area and the pore parameters of the materials. As listed in Table 1 and displayed in
CO2 performance of the SPISS samples under dry conditions.
The main objective of this study was to investigate how to manipulate processing of the sorbent materials containing the commonly used amine polymer bPEI, especially for application in DAC technology, and potentially induce enhanced CO2 adsorption performance. Hereon the discussion will focus exclusively on the 50% organic-loaded SPISS samples. As displayed in
To better understand the differences between the CO2 performance values, it was necessary to extract more information from the kinetic adsorption curves shown in
Under 10% CO2 conditions (
Under 400 ppm CO2 stream conditions, the 50% bPEI-SBA-15 sample had the highest rate value among all samples (
The SPISS samples were further subjected to temperature-swing adsorption-desorption kinetic cycles (TSA) to test their behavior under cycling conditions (Table 3).
Table 3 summarizes the TSA performance values recorded for the SPISS samples during this cycling. The highest CC values were recorded for 50% bPEI-SBA-15 SBL, 2.85 mmol CO2/gsio2 (10% CO2) and 2.60 mmol CO2/gsio2 (400 ppm CO2), associated with AE values of 0.13 mmol CO2/mmol N (10% CO2) and 0.12 mmol CO2/mmol N (400 ppm CO2), respectively. Intriguing was the CC value obtained for the 50% bPEI-SBA-15 SBD sample, 2.45 mmol CO2/gsio2 under the 400 ppm CO2 stream, similar to the 2.42 mmol CO2/gsio2 measured for the 10% CO2 stream. In addition, the AE values were similar and centered at 0.12 mmol CO2/mmol N.
Apparently, both blend and the non-blend SBL-processed samples had higher CC values than their SBD homologues under 10% CO2 conditions while the 50% bPEI-SBA-15 SBL scored the highest value under 400 ppm CO2 stream. All SPISS samples showed a robust steady behavior during TSA cycling that is of important practical relevance especially for DAC technologies. Such stable TSA behavior that does not cause thermal degradation or deactivation of amine sites is ideal for sorbent regeneration methods that involve elevated temperature. Altogether, the CO2 performance data gathered under continuous and TSA dry conditions could suggest that the processing methods influenced the morphology of the confined amine polymer.
CO2 adsorption performance of the SPISS samples under humid conditions.
In practical cycling under DAC conditions, the adsorption process needs to accommodate the presence of the moisture, as water is ubiquitously present in the air. It is known that water can compete with CO2 molecules during adsorption, leading to either increased (some amine materials) or decreased (most physisorbents) performance, as reported in the literature.64 The adsorption behavior of the water depends greatly on the sorbent type. From this perspective, it was important to test the CO2 performance of the SPISS samples using simulated, humid, ultra-dilute CO2 streams.
Prior to multicomponent adsorption experiments, water sorption by the SPISS samples was first evaluated with single component water adsorption experiments. In the dynamic vapor sorption (DVS) measurements the samples were subjected to pretreatment at 60° C. in a thermogravimetric analyzer (TGA from TA Instruments) until the relative humidity showed a null value. After a temperature ramp to 35° C., water was then added sequentially in isothermal sequences of 10% with equilibrations in between until a constant mass was achieved (<0.05%). As displayed in
Additional information about the water sorption behavior was extracted from the DVS curves (
Another useful piece of information extracted from the kinetic curves was the initial rate of water adsorption (
Once the water sorption behavior was investigated, the next step was to gather information about the CO2 performance of the SPISS samples under humid 400 ppm CO2 because, as mentioned above, these conditions have practical relevance to the DAC technology. For the purpose of accurate comparison between dry and humid conditions it was important first to test whether there were significant differences between dry CO2 adsorption determined gravimetrically (TGA) and using the fixed bed contactor (FB). As shown in
Under humid conditions (50% RH & 35° C.), all SPISS samples showed enhanced CC when compared with the dry conditions (
Insights into the dynamics of bPEI/LPPI polymer chains confined in SBA-15 channels. The data discussed in the preceding paragraphs could indicate that the processing of the SPISS samples, SBD vs. SBL and blends vs. use of PEI alone, influences their CO2 adsorption properties. These differences likely stem from different morphologies of the amine-containing polymers confined in the SBA-15 pores. Solid state NMR spectroscopy techniques were employed to investigate the correlation between molecular motion, morphology and mechanical relaxation processes. High-resolution 13C cross-correlation (CP) and high-resolution 13C direct-polarization (DP) Magic Angle Spinning (MAS) techniques were used to investigate whether the region of the recorded spectra associated with the aliphatic groups reflects structural differences as a function of sample composition and processing (
However, it should also be noted that chemical shifts in the solid state also depend on the conformation of the polymer chains. Especially conformations defined by different torsional angles of a carbon-carbon bond are known to lead to changes in the chemical shift in polymers (the gamma-gauche effect). The result is a significant broadening of line widths due to a distribution of possible torsional angles. Molecular motions around these torsional angles with frequencies larger than several kHz will lead to a motional averaging of line widths, i.e. narrower line widths corresponding to individual chemical sites and averaged torsional angles. The spectra displayed in
On the other hand, motions faster than ˜ 25 kHz can also lead to a significant reduction of the heteronuclear dipolar coupling constant between 13C and 1H and thus a slow buildup of the cross polarization, which will also reduce the intensity of the signal in the CP spectrum. However, motions with this frequency range should also lead to some motional narrowing detectable through the narrowing of an individual peak, which should be apparent in the DP spectra. Given the multitude of chemical sites and conformers, which all correspond to one individual peak, their overlap may still lead to a pattern apparently including only a few peaks. For the samples containing both polymers it was possible to record CP-spectra with a reasonable signal to noise ratio. Hence, in both cases, the presence of the LPPI leads to molecular dynamics at presumably lower frequencies associated with more favorable conditions for the CP experiment.
The second striking difference between the individual 13C-MAS spectra is the presence of a peak/shoulder at ˜30 ppm, which is prominently observed in the DP (
Hence, we hypothesize that the presence of LPPI in the blend samples also improves the ordering of bPEI. During mixing of the two polymers, LPPI can better bridge the bPEI, ‘smoothing’ the interfaces between the two polymers. However, it is obvious that the observed variation in spectral features as a function of processing suggests that packing of polymer chains is different for the samples under investigation.
The findings of this study indicate that the processing during sample synthesis was the key factor that influenced the morphology of the two amine polymers confined in the pores and induced enhanced adsorption properties in some cases. The NMR experiments further support this hypothesis and begin to unravel important insights about the mobility of the bPEI and LPPI polymers residing under pore confinement. It is reasonable to assume, based on classical polymer dynamics theories, 65, 66 that likely bPEI and LPPI, due to their different conformations (branched versus linear), did not mix well in the channel; rather, they were segregated to some degree. At the same time, bPEI and LPPI behave as molecular crowding entities67 for each other, and within each (polydispersity effects), leading to multiple interfacial interactions (heterogeneity effects). These interactions, most likely entropic in nature, forced the segregated polymers to adjust their conformation by better aligning and ordering, especially when the solvent was evaporated.68 These observations are in line with the views published in a comprehensive perspective by Chandran et al. stating that rapid processing induce nonequilibrium molecular conformations of polymers and subsequently lead to structural, dynamical and mechanical properties different from those in thermodynamic equilibrium.69
Two consecutive solvent evaporation steps during the SBD method likely led to a tightly packed bulk conformal bPEI layer at the channel inner wall sequentially coated by thin layers of intermixed/segregated bPEI for non-blends and bPEI/LPPI for blends (
From the standpoint of understanding the structure-processing-property relationship of these sorbents, it is important to connect the observed properties to the unraveled different morphology of bPEI/LPPI generated by the two processing approaches. If one takes in consideration the most important metric, amine efficiency (AE), both blends 50% LPPI-bPEI-SBA-15 SBD and 50% LPPI-bPEI-SBA-15 SBL were more efficient under 10% CO2 while only the latter was more efficient under 400 ppm CO2 conditions. The high initial rates observed for the SBL-processed samples, especially under dry 10% CO2, correlate with a loose packing that likely favors fast kinetics (fast diffusion and amine-site access,
If the above assumptions for the dry one-component conditions are true, then opposite trends would be expected for the multicomponent humid experiments. In the DVS experiments, it was not surprising that the 50% bPEI-SBA-15 SBL sample adsorbed the most water (8.85 mmol H2O/gsio2), substantially higher than the 50% bPEI-SBA-15 SBD analogue (5.02 mmol H2O/gsio2). Because the samples had similar pore filling (Table 1), it is obvious that the different volume occupied by water was associated with tight vs. loose morphology of the polymer chains in the channel. A less compact morphology like in 50% bPEI-SBA-15 SBL, allowed better exposure of the amine sites for interaction with the adsorbate molecules. Second, once adsorbed in sufficient amounts, water can occupy the amine sites, making them less accessible to CO2 during humid multicomponent adsorption experiments.64 Regardless of the used metric AE or CC, 50% bPEI-SBA-15 SBD sample was markedly more effective under 400 ppm CO2 humid stream, this could be due to its dense packed morphology allowed for less water sorption that did not as greatly compete with CO2 adsorption than the 50% bPEI-SBA-15 SBL homologue (
Samples including of branched polyethylenimine (bPEI, Mw=800 Da) and blends with linear polypropylenimine (LPPI, Mw=6,700 Da) were prepared by a method referred to as sequential polymer infusion into solid (SBA-15) substrates (SPISS). The purpose of this approach was twofold: (I) to enhance the CO2 adsorption properties by varying the solution processing and (II) to probe whether the presence of hydrophobic LPPI can limit water uptake. A 40 wt % bPEI reference sample was prepared for each synthesis that was split in a 50:50 ratio. Splitting was performed in two ways: via a dry suspension (SBD) and a liquid suspension (SBL). Sequentially, alcoholic 10% bPEI for non-blends and alcoholic 10% LPPI for blends were added and the solvent was evaporated.
The 50% bPEI-SBA-15 SBL & SBD and 50% LPPI-bPEI-5 SBL & SBD samples displayed high CO2 uptake when compared to literature reports under both simulated flue gas (10% CO2) and DAC (400 ppm CO2) conditions. The initial rate of adsorption revealed that in the SBL-processed samples the amine sites were faster accessed by the CO2 molecules than in SBD-processed analogues, likely due to different polymer morphologies in the samples. Subjected to extended temperature-swing adsorption-desorption kinetic cycling (TSA, 20 cycles), the SBL-processed samples displayed higher CC than their SBD analogs for both 10% CO2 and DAC conditions. The SPISS samples had stable working capacities with no apparent deactivation over the extended TSA cycles.
Dynamic vapor sorption measurements showed that LPPI limited the water uptake of the sorbents that contained blends of aminopolymer. The amount of water adsorbed by the 50% bPEI-SBA-15 SBL & SBD samples that was extracted from the CO2 sorption kinetic curves at 50% RH again supported the hypothesis that different processing conditions impacted the morphology of the polymers in the pores. All samples showed enhanced CO2 adsorption under the conditions relevant to DAC technology. Comparison between the CO2 uptake of the pre-humidified 50% bPEI-SBA-15 SBL & SBD samples provided additional support to the idea that the morphology of the polymers in the SBA-15 channels is essentially different.
Solid state 13C NMR cross-polarization magic angle spinning (CP) and direct polarization magic angle spinning (DP) studies confirmed that the conformations of the bPEI in non-blends and the conformation of bPEI and LPPI in blends are different. The results indicated that polymer chains crowded each other and underwent ordering to differing degrees. In the SBD samples, polymer packing was tight while in the SBL samples packing was loose, with the later condition potentially aiding CO2 sorption.
Altogether the data demonstrate that altering solution processing can identify conditions where polymer non-blends and blends give sorbents with improved overall CO2 performance. The main findings showed that ordering of the active amine molecules can be a key factor in enhancing CO2 adsorption properties. Equally important is the nature of the additive species (e.g. LPPI) that altogether with the process-induced morphology can fine tune the desired adsorption properties. This study is relevant for the preparation of amine sorbents with enhanced CO2 performance and their integration into CO2 capture technologies.
Branched polyethylenimine (bPEI, Mw=800), tetraethyl orthosilicate (TEOS, reagent grade, 98%), pluronic P-123 (EO:PO:EO, Mn=5800 Da), hydrochloric acid (HCl, ACS reagent, 37%), and methanol (MeOH, for HPLC, ≥99.9%) were purchased from Sigma-Aldrich and used as received. UHP He, 400 ppm CO2/He and 10% CO2/He gases were procured from Airgas. Linear polypropylenimine (LPPI, Mn=6700 Da) was available in the laboratory and also used in a previous report. 42, 71
The organic content of the samples was evaluated by using a TGA 550 Discovery Series from TA Instruments. Data were recorded at a scan rate of 20° C./min under N2 (90 mL/min) from room temperature to 700° C. The organic content was calculated from the 150° C.-600° C. temperature range.
The elemental content of C, H, and N was determined by Atlantic Microlabs (Norcross, GA). The N content expressed in mmoles was calculated from the repeat unit formulae of both bPEI and LPPI and from the percentage contribution of each element from elemental analysis as well as the atomic mass of N. The calculated values were normalized per gram of silica support.
A Micromeritics Tristar II instrument was used for recording isotherms at 77 K. Prior to the analysis, the samples were subjected to pretreatment in a high-vacuum line operating at ˜10 mtorr for 12 h at 100° C. The surface area was determined by applying the BET theory in the 0.05-0.2 P/Po pressure range. The total pore volume was calculated based on the amount of N2 adsorbed at P/Po of 0.95 using the formula
Where 1.2504 is the density of N2 (g/cm3) at standard temperature and pressure conditions and 807 is the density of N2 (g/cm3) at its boiling point.
A Q500 TGA apparatus (TA Instruments) was used to measure CO2 adsorption capacities of the SPISS samples. The samples were first subjected to pretreatment by heating to 110° C. under He (90 mL/min) at a 10° C./min rate and held isothermally for 2 h to remove adsorbed ambient CO2 and moisture. The samples were then cooled to 35° C. at the same rate and equilibrated for 1 h under helium. Then the inlet gas was switched to either 10% CO2/He or 400 ppm CO2/He (90 mL/min) and the samples were kept isothermal for 12 h. The recorded final mass used in the CO2 adsorption capacity was normalized by the initial mass after 2 h pretreatment at 110° C. Two samples were tested in a custom-built fixed bed as will be discussed in a below paragraph. The purpose was to test reproducibility data between the two methods of recording CO2 capacity. Statistical analysis of the calculated initial rates values variance was performed by ANOVA platform from Origin 2016. The general equation used by Anova is:
where the denominator represents the degree of freedom, the summation is the sum of squares, the squared terms are the deviations from the variable mean and the result is the mean square.
These experiments were performed in the same instrument as described above and following the same program segment for pretreatment: isothermal for 2 h at 110° C. and 1 h at 35° C. under He. Afterward, repeat cycles (20) of isothermal adsorption (35° C. for 1 h under CO2/He (10% or 400 ppm)) and isothermal desorption (90° C. for 10 min under He) were performed, allowing 10 min equilibration time at the adsorption temperature before gas switching.
A custom-built fixed bed set up was used to measure the CO2 performance of the 50% organic loading SPISS samples. About 50 mg the sample was grinded to fine powder. A pelletizer was used to pelletize the powders by applying a pressure of 1000 psi for 30 seconds. The resulting pellets were crushed and sieved through a 300-600 μm sieve to afford particles of precise size. About 25 mg of sieved sample was encased in a ¼ inch diameter glass tube and supported by a bed of glass wool. The packed bed was activated in nitrogen (90 mL/min) at a temperature of 90° C. until there was no trace of CO2 and H2O downstream as indicated by a calibrated Li 840A CO2/H2O gas analyzer (LiCOR). The temperature of the bed was reduced to 35° C. The bed was then pre-saturated with a 50% RH nitrogen carrier gas until the H2O concentration downstream was stable. Afterward, the bed was exposed to humid 400 ppm CO2 balanced by nitrogen (50% RH) at a flow rate of 50 mL/min, and the increasing CO2 concentration was monitored as a function of time until equilibrium was reached. Once the CO2 concentration was stable, the temperature was ramped up to 90° C. in dry nitrogen for desorption. The procedure detailed here was repeated with an empty glass tube. An integral area between the two normalized breakthrough curves (glass tube—no sample; glass tube—with sample) was used to calculate the humid CO2 adsorption capacity and amine efficiency.
A TGA Q5000 instrument (TA Instruments) equipped with a humidity module was used for the dynamic vapor sorption experiments. The SPISS samples were pretreated first at 60° C. for at least 1 h under dry nitrogen (200 mL/min) and until the sample RH sensor indicated null humidity. The temperature was decreased to 35° C. and equilibrated for 10 min. Then the humidity was set at 10% and the sample was kept isothermal for at least 1 h and until the humidity sensor indicated a percentage weight change <0.0500 for 5.00 min. For the adsorption part of the curve, this segment was repeated by sequentially adding 10% humidity until the maximum 100% RH. The desorption curve was obtained by the repeat program step with the difference that the humidity was decreased sequentially by 10% until reached the minimum of 0% RH.
13C solid state NMR spectra were recorded under condition of magic angle spinning (MAS) on a Bruker AV3-300 HD operating at a 1H frequency of 300 MHz. Samples were packed in 4 mm O.D. rotors and spun with a frequency of 10 kHz. 13C CP spectra were recorded using standard conditions; a ramp-shaped contact pulse for 1H during a contact time of 3 ms and a repetition delay of 4 seconds and high power decoupling. 13C DP spectra were recorded under identical conditions of decoupling with a repetition delay of 5s.
SBA-15. Mesoporous SBA-15 was synthesized by following a previously reported procedure.42
SPISS SBD samples.
The SPISS samples were prepared by sequential bPEI (Mw=800 Da)/LPPI (Mn=6700 Da) infusion into the SBA-15 solid substrate by using two solution-processing approaches: split batch dry suspension (SBD) and split batch liquid suspension (SBL). The synthesis started with the preparation of the reference 40% bPEI-SBA-15 sample, a common step for SBD and SBL. In a typical reference synthesis, 500 mg of SBA-15 were suspended in 20 mL methanol (MeOH) in a 100 mL round-bottomed flask and sonicated for 30 min until a homogeneous suspension formed. Separately, bPEI (40 wt % with respect to the total mass (PEI+SBA−15)) was dissolved in 10 mL MeOH inside a 20 mL scintillation vial that was capped and the solution was magnetically stirred for 30 min. Afterward the PEI/MeOH solution was added to the flask containing SBA-15/MeOH and the suspension was magnetically stirred overnight. Then the reference sample was processed differently for the two approaches mentioned above. Four reference samples were necessary for this study, two for SBD and two for SBL. For SBD, the solvent from the reference sample was evaporated by using a rotary evaporator equipped with a water bath operating at 50° C. The resulting powder was then split in half (50:50). One half was kept as standard and the other half was suspended in a premade alcoholic (MeOH) solution of either 10% bPEI or 10% LPPI each dissolved in 10 mL solvent. The suspension was stirred overnight and the solvent was evaporated affording a fine white powder product. For SBL, the reference samples were split each in liquid suspension state (50:50) after vigorous shaking. Like SBD, one half was kept as standard and dried by rotary evaporation, and the other half was mixed with the 10% bPEI/MeOH and 10% LPPI/MeOH and stirred overnight. A fine white powder was obtained after solvent evaporation. All samples were subsequently dried in a high vacuum (˜10 mtorr) at 60° C.
Preparation of improved CO2-philic phase sorbents containing polypropylenimine (PPI) and polyethylenimine (PEI) Branched polyethylenimine (PEI), MW 800 was purchased from Sigma Aldrich. Polypropylenimine (PPI), MW 1200, was synthesized and sourced from a partner manufacturer Celares. Samples for each of titania and alumina were made. The PEI was dissolved in a solution of methanol, after which the PPI was added. PPI was added in ratios corresponding to 0.1 and 0.75 mol PPI per mol of N present in PEI. Separately, a mesoporous titania or alumina was dispersed in methanol and mixed until homogeneous. Then, the PEI/PPI mixture was pipetted into the titania or alumina/methanol dispersion. After stirring for >3 h the solvent was removed by rotary evaporation and subsequent drying in a vacuum oven at 100° C. Mass ratios of the titania or alumina and PEI/PPI were controlled such as to achieve 50-70% filling of the mesopores of the mesoporous titania or alumina with PEI/PPI mixture. The resultant composite sorbents were of a powdery consistency.
Chemical Characterization of improved CO2-philic phase sorbents containing polypropylenimine (PPI) and polyethylenimine (PEI)
Chemical characterization was carried out to confirm the properties of the improved CO2-philic phases. TGA burnoff experiments were carried out on sorbents comprised of the improved CO2-philic phases to characterize the total quantity of organic present in the sorbent. Samples were heated under diluted air to 900° C. and their mass loss tracked. Total organic content was taken as the mass loss over that temperature interval, after removing the contribution of CO2 and H2O lost at lower temperatures.
Sorbents created with improved CO2-philic phases were tested for CO2 adsorption in a TGA under 400 ppm CO2 at 30° C. in dry and humid conditions to simulate the gas contacting step of a Direct Air Capture process. For dry experiments, the sorbents were first treated in N2 at 100° C. to desorb any bound H2O and CO2 before being equilibrated at 30° C. under N2. Then, the gas concentration was switched isothermally to contain 400 ppm CO2 balanced by N2 and the mass change was recorded. Under these moisture free conditions, the mass gain of the material corresponds to the adsorption of CO2 and therefore can be used to measure the total quantity and rate of CO2 adsorption onto the materials. For humid experiments, the sorbents were first treated in N2 at 100° C. to desorb any bound H2O and CO2 before being equilibrated at 30° C. under humidified N2. Then, the gas concentration was switched isothermally to contain humidified 400 ppm CO2 balanced by N2 and the mass change was recorded. To humidify the N2 and 400 ppm CO2 balance N2 gases, the gas was saturated with water vapor at a dew point of 10° C. by sparging the gas stream in a water bath held at 10° C. Under these humid conditions, it is assumed that no additional water is adsorbed between switching from a humidified N2 stream to a humidified CO2 and N2 stream, and thus the mass gain of the material corresponds to the adsorption of CO2 and therefore can be used to measure the total quantity and rate of CO2 adsorption onto the materials.
Various improved sorbents were characterized for CO2 adsorption using these methods and compared to the baseline PEI and PPI based sorbents.
The sorbents were evaluated on two bases, i) CO2 capacity, mmol of CO2 adsorbed per mmol of sorbent present, and ii) amine efficiency, mmol of CO2 adsorbed per mmol of N present. The former unit of performance is useful to show bulk sorbent performance, and the second unit of performance is useful to evaluate the performance of the amine polymer itself and takes into account changes to the bulk composition of the sorbent.
The oxidative stability of materials can be probed in several ways.
In this study, the oxidative stability of the sorbents was evaluated by tracking the heat flow evolved from the materials using a DSC during exposure to isothermal oxidative conditions. Here, the sorbents were first treated in inert gas at 100° C. to desorb any bound H2O and CO2 before being equilibrated at 137.5° C. under inert gas for 60 minutes. The gas was then isothermally switched to a 17% O2 mixture and held until the reaction finished. This isothermal, oxidative environment was maintained for a specific amount of time to measure the heat flow and mass loss. To prevent any further oxidation, the sample was then cooled under N2 to room temperature. During these experiments, for each oxidative condition, the DSC measures the incremental heat flux, which increases, levels out, and then decreases to zero. The oxidation was considered complete when the integrated heat flow over 10 min changed less than +0.01% of the total integrated heat. To determine the extent of oxidation as a function of time, DSC data were converted from the base unit of mW/mg sorbent to W/gPEI using the PEI loading measured by TGA burnoff. DSC data were corrected for drift by applying an offset, determined by the heat flow value when the DSC curve approached a horizontal line. The total heat evolved was calculated by integrating heat flow over time. The extent of oxidation from DSC was calculated by dividing the integral heat flow curve by the total heat evolved. This method has been previously calibrated with the loss in amine efficiency as being a method of tracking the chemical reaction rate of oxidative degradation in-situ and is shown in
Evaluating the oxidative stability of materials in environments that contain oxygen and CO2 is useful due to the fact that during regeneration processes, desorbed CO2 is present at different concentrations in addition to oxygen at elevated temperatures and can impact the stability of the material. Separately, evaluating the oxidative stability of materials with oxygen only (air) is a useful way to evaluate the shelf life of a material when it is stored at ambient conditions.
It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of “about 0.1 percent to about 5 percent” should be interpreted to include not only the explicitly recited concentration of about 0.1 weight percent to about 5 weight percent but also include individual concentrations (e.g., 1 percent, 2 percent, 3 percent, and 4 percent) and the sub-ranges (e.g., 0.5 percent, 1.1 percent, 2.2 percent, 3.3 percent, and 4.4 percent) within the indicated range. The term “about” can include traditional rounding according to significant figures of the numerical value. In addition, the phrase “about ‘x’ to ‘y’” includes “about ‘x’ to about ‘y’”.
Many variations and modifications may be made to the above-described aspects. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.
This application claims priority to U.S. provisional application entitled “SORBENTS, SYSTEMS INCLUDING SORBENTS, AND METHODS USING THE SORBENTS” having Ser. No. 63/457,426 filed on Apr. 6, 2023, which is entirely incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63457426 | Apr 2023 | US |
