Patent Application
20250033027
Supported polyamine compositions are provided based on high pore volume supports, along with methods of forming and using the compositions.
One strategy for performing CO2 capture is to perform a process cycle where CO2 is first sorbed using a solid sorbent, and then desorbed in a subsequent part of the cycle. This can allow CO2 to be selectively removed from a gas flow. A variety of amines have been previously investigated for potential use as sorbent materials for CO2 capture.
One difficulty with using amines is balancing the various considerations that are desirable for a sorbent material. Preferably, a sorbent material can have a relatively low cost of manufacture, a high sorption capacity per weight/volume of the material, and a long operating lifetime before breakdown and/or degradation. It would be desirable to develop materials with improved combinations of these features.
Another difficulty is providing the amine in an environment that allows for efficient exposure of the amine to a CO2-containing gas (such as air) in an efficient manner while maintaining a substantial majority of the sorption capacity. Conventionally, for CO2 sorbent materials that require a support to provide a solid structure, a common technique is to support the sorbent on a high surface area support. The support can optionally be deposited on a structural material, such as a monolith, to provide a geometry that assists with exposing a gas flow to the sorbent. However, for polyamines such as polyethyleneimine, supporting the polyamine on a high surface area support typically results in a substantial loss of sorbent capacity on a CO2 sorption per gram basis.
A journal article titled “Epoxy Cross-Linked Polyamine CO2 Sorbents Enhanced via Hydrophobic Functionalization” (Chem Mater. Vol. 31, No. 13, p 4673, 2019) describes modification of polyethyleneimine with hydrophobic additives, such as 2-ethylhexyl glycidyl ether. The modified polyethyleneimine is then cross-linked using bisphenol-A diglycidyl ether to form a support-free sorbent material. These materials are shown to be able to tune adsorption efficiency, but do not take into account operating lifetime.
A journal article by Choi et al. titled “Epoxide-functionalization of polyethyleneimine for synthesis of stable carbon dioxide adsorbent in temperature swing adsorption” (Nat. Commun. 7:12640 doi: 10.1038/ncomms 12640 (2016)) describes assignment of primary, secondary, and tertiary amines using 13C NMR spectroscopy.
Some review articles have provided overviews of recent efforts to form sorbent systems based on polyethyleneimine supported on mesoporous silica. One review is “Stability of Amine-Functionalized CO2 Adsorbents: A Multi-Faceted Puzzle”, (Lashaki et al., Chem. Soc. Rev. 2019 48 3320). Another review is “Direct Capture of CO2 from Ambient Air”, (Sanz-Perez et al., Chem. Rev. 2016 116 11840).
Other journal articles have focused on specific systems, such as supporting polyethylene imine on zeolite 13X or ZSM-5. An example of such an article is “Polyethyleneimine-incorporated Zeolite 13X with Mesoporosity for Post-Combustion CO2 Capture”, (Chen et al Appl. Surf. Sci. 2015 332 167). Another example is “Effects of Pore Structure and PEI Impregnation on Carbon Dioxide Adsorption by ZSM-5 Zeolites”, (Lee et al., J. Industrial Eng. Chem. 2015 23 251). Still another example is “Polyethyleneimine-Modified Zeolite 13X for CO2 Capture: Adsorption and Kinetic Studies”, (Karka et al., ACS Omega 2019 4 16441).
U.S. Pat. No. 10,807,875 describes synthesis of certain types of zeotype frameworks.
In an aspect, a supported amine sorbent is provided. The supported amine sorbent includes a support material containing silica and alumina, the support material being crystalline. The support material can have a pore volume of 0.20 g/cm3 or more, a ratio of mesopore volume to micropore volume of 1.0 or more, a total surface area of 100 m2/g or more, a ratio of Si to Al2 of 10-1000, and/or an acidity as measured by temperature programmed ammonia desorption of 0.10 meq/g or more. The supported amine sorbent further includes 30 wt % to 80 wt % of a polyamine supported on the support material, relative to a weight of the support material.
In another aspects, a supported amine sorbent is provided. The supported amine sorbent includes a support material containing silica and alumina. The support material can have a pore volume of 0.20 g/cm3 or more, a ratio of mesopore volume to micropore volume of 1.0 or more, a total surface area of 100 m2/g or more, a ratio of Si to Al2 of 50-1000, and an acidity as measured by temperature programmed ammonia desorption of 0.10 meq/g or more. The supported amine sorbent further includes 30 wt % to 80 wt % of a polyamine supported on the support material, relative to a weight of the support material.
In various aspects, crystalline support materials are provided that can serve as supports for polyamines. The support materials have a combination of properties that unexpectedly allows supported polyamines to retain an increased or maximized amount of CO2 sorption capacity after incorporation of substantial amounts of the polyamine on the support material. This combination of properties can include having a high pore volume, a high ratio of mesopore volume to micropore volume, and a sufficiently high acidity. The ability to allow supported amine sorbents to retain additional CO2 sorption capacity is unexpected. Conventionally, even when high pore volume support materials are used to support an amine sorbent, only a limited amount of the amine sorbent can be supported on the support material before substantial losses of sorbent capacity occur relative to the amount of amine sorbent.
It has also been discovered that the support materials having high pore volume, high ratio of mesopore volume to micropore volume, and sufficiently high acidity can retain the advantage of facilitating sorption by supported amines when the supported amines are deposited on a support structure, such as a monolith.
Crystalline support materials, such as support materials having a zeotype framework structure, always have at least some micropore volume due to pore channels within the crystalline material. For most crystalline materials, however, it is unusual to have both high pore volume and a high ratio of mesopore pore volume to micropore pore volume. For materials such as MCM-41 that do have relatively high mesopore volumes, the acidity of the material is typically relatively low.
A variety of amine-based sorbent materials are available that have high sorption capacity for CO2. However, to use such sorbent materials for CO2 sorption on a commercial scale, the sorbent materials either have to be self-supporting, or the sorbent materials have to be supported on another material. While it is feasible to use some amine-based materials as self-supported structures, there is typically a substantial reduction in CO2 sorption capacity relative to laboratory scale sorption tests. This is due in part to difficulties in allowing a CO2-containing gas to reach the full volume of the self-supporting structure. Thus, it would be desirable to have support materials that can support amine-based sorbents while retaining a higher percentage of the potential sorption capacity of the amine-based sorbent. Additionally, it would be desirable to be able to achieve a high loading of amine-based sorbent relative to the weight of the support material, so that the resulting supported amine-based sorbent has a high CO2 sorption capacity per unit volume.
In this discussion, a zeotype is defined to refer to a crystalline material having a porous framework structure built from tetrahedra atoms connected by bridging oxygen atoms. Examples of known zeotype frameworks are given in the “Atlas of Zeolite Frameworks” published on behalf of the Structure Commission of the International Zeolite Association”, 6th revised edition, Ch. Baerlocher, L. B. McCusker, D. H. Olson, eds., Elsevier, New York (2007) and the corresponding web site, http://www.iza-structure.org/databases/. Under this definition, a zeolite refers specifically to an aluminosilicate having a zeotype framework structure. Under this definition, a zeotype can refer to aluminosilicates (i.e., zeolites) having a zeotype framework structure as well as zeotype framework structures containing oxides of atoms different from silicon and aluminum. Such oxides can include oxides of any other atoms generally known to be suitable for inclusion in a zeotype framework, such as oxides gallium, boron, germanium, phosphorus, zinc, and/or other transition metals that can substitute for silicon and/or aluminum in a zeotype framework. It is noted that under this definition, a zeotype can include materials such as silicoaluminophosphate (SAPO) materials or aluminophosphate (AlPO) materials.
In this discussion, crystalline materials are defined as materials that have an ordered microscopic structure that is capable of diffracting X-rays. Crystalline materials can include, but are not limited to, zeotypes (i.e., materials having a zeotype framework structure) and clays that have sufficient long-range order to be capable of diffracting X-rays. Examples of crystalline zeotypes can include zeolites (materials composed of silicon, aluminum, and oxygen) and SAPOs (materials composed of silicon, aluminum, phosphorus, and oxygen). Examples of atoms different from silicon, aluminum, and oxygen that can be present in a material having a zeotype framework structure include, but are not limited to, Ge, Ga, B, P, and Zn.
In this discussion, a “hierarchical structured zeotype” material is defined as a zeotype material (having a zeotype framework structure) that has at least two levels of pore diameters. A first level of pore diameters corresponds to pores with diameters of less than or equal to 2.0 nm, while the second level of pore diameters corresponds to pores with diameters greater than 2.0 nm. In other words, hierarchical structured zeotypes not only have inherent microporosity, but also have mesoporosity or even macroporosity. Such hierarchical structured materials typically have crystal sizes of less than 1.0 microns. It is noted that although materials such as MCM-41 and MCM-48 have mesoporous channels that are defined as part of the corresponding zeotype framework structure, such materials lack microporosity, and therefore are not inherently within the definition of hierarchical structured zeotype materials.
In this discussion, references to a periodic table are defined as references to the current version of the IUPAC Periodic Table.
In this discussion, the term “polyamine” is defined to include polyamines that include other functional groups, such as polyhydroxylamines or functionalized polyamines. Thus, a modified polyamine that is modified by cross-linking with a cross-linker as described herein also falls within the definition of a polyamine.
One property of a support material is a high pore volume. In various aspects, a support material can have a pore volume of 0.20 g/cm3 or more, or 0.25 g/cm3 or more, or 0.30 g/cm3 or more, or 0.50 g/cm3 or more, such as up to 1.0 g/cm3 or possibly still more. In this discussion, pore volume is BET pore volume determined according to ASTM D6761. High pore volume can potentially be beneficial for providing additional surface area for the polyamine sorbent. However, conventional attempts to support polyamines on high pore volume supports have taken into account other factors that impact the sorption capacity of the supported polyamine.
In addition to having a sufficient pore volume, a support material can have one or more additional properties. In some aspects, a support material can have an average pore diameter between 5.0 nm and 200 nm, or 5.0 nm to 150 nm, or 5.0 nm to 100 nm, or 5.0 nm to 50 nm, or 10 nm to 200 nm, or 10 nm to 150 nm, or 10 nm to 100 nm, or 10 nm to 50 nm. Average pore diameter is calculated as 4V/A, where V is the BET pore volume and A is the BET total surface area, as determined according to ASTM D6761. Total area is determined according to ASTM D4365. Without being bound by any particular theory, it is believed that larger pore volumes facilitate access of the additional surface area by polyamines.
Another potential consideration is the ratio of mesopore volume to micropore volume. In some aspects, a support material can have a mesopore volume that is equal to or greater than the micropore volume. In such aspects, the ratio of mesopore volume to micropore volume can be 1.0 or more, or 1.2 or more, or 1.5 or more, such as up to 2.5 or possibly still higher. In this discussion, mesopores are defined as pores having a pore diameter of roughly 2 nm to 50 nm. It is noted that ASTM D4365 also provides mesopore volume, which therefore allows for calculation of micropore volume by subtracting the mesopore volume from the total pore volume. Without being bound by any particular theory, it is believed that having a high mesopore volume relative to the micropore volume facilitates allowing the polyamine to enter pores while reducing or minimizing clogging of pores that would restrict sorption capacity.
It is noted that mesopore volume can be provided in at least two ways. Some mesopore volume can correspond to mesopores that are defined by the structure of an individual crystallite. In other words, an individual crystal can have one or more pores that are sufficiently large to qualify as mesopores. Other mesopore volume can correspond to mesopores that are defined by the spacing between adjacent crystals. As the size of crystals in a sample is reduced, an increasing amount of mesopore volume can correspond to mesopore volume between crystals that have a hierarchical structure.
Still other factors can be related to the available surface area. Materials with increased surface area can potentially distribute a given amount of an amine sorbent over a larger area, allowing for a thinner layer of amine supported on the material. However, it has been discovered that total surface area alone does not indicate whether a material can provide improved performance for retaining CO2 sorption capacity when used as a support for a supported amine. Instead, the ratio of external surface area to total surface area is also relevant. In some aspects, a support material can have a total surface area of 100 m2/g or more, or 200 m2/g or more, such as up to 600 m2/g or possibly still higher. Additionally or alternately, a support material can have a ratio of external surface area to total surface area of 0.15 or more, or 0.20 or more, or 0.25 or more, such as up to 0.50 or possibly still higher.
Yet another factor can be the ratio of silicon to aluminum in the support material. Examples of ranges for Si to Al2 include 10-1000, or 10-300, or 10-150, or 10-100, or 10-49, or 10-30, or 30-1000, or 30-300, or 30-150, or 30-100, or 50-1000, or 50-300, or 50-150. For crystalline materials such as zeolitic materials, the ratio of Si to Al2 (silica to alumina) in the crystalline material can be 1000 or less, or 300 or less, or 150 or less, or 100 or less, such as down to 10 or possibly still lower. In some aspects, a crystalline support material with a hierarchical structure and/or a crystal sizes too small to resolve with X-ray diffraction can have a Si to Al2 ratio of 50 or more. For amorphous silica-alumina materials, in some aspects the amorphous silica-alumina can include 20 wt % or more of silica relative to a weight of the amorphous silica-alumina, or 30 wt % or more, such as up to 90 wt %. In some aspects, the amorphous silica-alumina can include 10 wt % or more of alumina, or 20 wt % or more, such as up to 80 wt %. In addition to silica and alumina, the amorphous silica-alumina can include 15 wt % or less of oxides different from silica and alumina, or 10 wt % or less, such as down to being substantially composed of silica and alumina. In other words, the amorphous silica-alumina can have a combined weight of silica and alumina of 85 wt % or more relative to a weight of the amorphous silica-alumina, or 90 wt % or more, such as up to being substantially composed of silica and alumina. In some aspects, a support material (crystalline or amorphous) can consist essentially of oxides of silicon and aluminum, so that less than 1.0 wt % of the material corresponds to atoms different from silicon, aluminum, and oxygen, or less than 0.1 wt %, such as down to no heteroatom content.
Still another factor can be the acidity of a material. In some aspects, a support material can have an acidity, as measured by temperature programmed ammonia desorption (TPAD), of 0.10 meq/g or more, or 0.15 meq/g or more, such as up to 0.50 meq/g or more.
Support materials that can satisfy a plurality of the above properties may or may not have an X-ray diffraction (XRD) pattern that shows long range order and/or crystallinity. Some materials may correspond to crystalline zeotype materials (such as zeolitic materials) that have a zeotype framework structure. Other materials may correspond to small crystal zeotype materials and/or hierarchical materials that have broadened XRD patterns due to small crystal size.
In some aspects, the support material can correspond to a zeotype material (i.e., a material having a zeotype framework structure). In such aspects, the zeotype material can have a pore network so that a diffusing sphere of 5.0 Angstroms or larger can pass through the pore network, such as up to 10 Angstroms or possibly still larger. Additionally or alternately, the zeotype material can have largest pore channel having a ring size corresponding to a 10-member ring or larger, such as up to a ring size corresponding to a 16-member ring. Further additionally or alternately, the zeotype material can have pore volume of 0.2 cm3/g or more, such as up to 0.5 cm3/g or possibly still more. Still further additionally or alternately, the zeotype material can have a ratio of mesopore volume to micropore volume of 1.0 or more, such as up to 2.5. Such a zeotype material may optionally not have substantial Bronsted acidity.
Support materials that can have a plurality of the above characteristics, such as three or more, or four or more, and up to substantially all of the above characteristics, include crystalline materials (such as zeotype materials), as well as small crystal/hierarchical versions of crystalline materials. Examples of crystalline materials having zeotype framework structure that can have combinations of the above properties include EMM-57, EMM-72 (SFN), EMM-34 (MOR), EMM-20 and/or ZSM-5 (MFI), UTD-1 (DON) and EMM-30 and/or ZSM-11. Examples of zeotype materials that can have combinations of the above characteristics in small crystal/hierarchical versions include zeolite Beta (BEA), mordenite (MOR), ZSM-12 (MTW), ZSM-5 (MFI), UTD-1 (DON), ZSM-23 (MTT), and ZSM-57 (MFS).
Formation of High Pore Volume Support with Supported Amine-Based Sorbent
The support material can be used to support an amine-based sorbent, such as a sorbent suitable for sorption of CO2. The sorbent material can include primary amines, secondary amines, tertiary amines, or a combination thereof. The number average molecular weight of the sorbent material can range from 200 g/mol (equivalent to Daltons) to 1,000,000 g/mol, or 200 g/mol to 100,000 g/mol. Polyethyleneimine (PEI) is an example of a suitable polyamine. Other types of polyamine polymers (including polyimines) can also be used, such as polyhydroxylamine. Still other examples of polyamines include, but are not limited to, polyvinylamine, polypropyleneimine, polyallylamine, poly(2-dimethylaminoethyl acrylate), poly(2-dimethylaminoethyl methacrylate) and other vinyl polymers. Such polymeric materials can be branched or unbranched. In some aspects, the polyamine can correspond to a functionalized polyamine, such as a polyamine that has been cross-linked. For example, a polyamine can be reacted with a multi-dentate linker to form a cross-linked polyamine material.
In some aspects, the polyamine can correspond to a low molecular weight polyamine. For example, a low molecular weight polyamine can have a weight average molecular weight of 500 Da (Daltons) to 15,000 Da, or 500 Da to 10,000 Da, or 500 Da to 5,000 Da, or 500 Da to 2,000 Da, or 500 Da to 1,500 Da. Additionally or alternately, the low molecular weight polyamine can have a number average molecular weight of 500 Da (Daltons) to 5,000 Da, or 500 Da to 2,500 Da, or 500 Da to 1,300 Da, or 500 Da to 1,000 Da. It is noted that for many types of polymers, there is a difference between the number average molecular weight and the weight average molecular weight (i.e., polydispersity). Polydispersity is defined as the ratio of the weight average molecular weight divided by the number average molecular weight. In some aspects, the polydispersity for the polyamine can be 1.5 or less, or 1.4 or less, or 1.3 or less, such as down to 1.0 (i.e., having substantially no polydispersity).
In various aspects, a supported sorbent can be formed by supporting an amine-based sorbent on a high pore volume support material as described herein. In aspects where the high pore volume support material corresponds to a zeolitic material, the support material can be calcined in air to remove the structure directing agent (SDA) and/or pre-calcined in inert atmosphere, ammonium exchanged, and re-calcined in air to create the acid form of the material. Once the acid form of the zeolite is created an amine-based sorbent can be loaded on to the support.
In various aspects, the loading of amine-based sorbent on the support can correspond to 30 wt % relative to the combined weight of sorbent and support material, or 40 wt % or more, or 50 wt % or more, such as up to 75% or possibly still higher. In some aspects, the loading of amine-based sorbent on the support can be 30 wt % to 75 wt % relative to the combined weight of the sorbent and support material, or 30 wt % to 60 wt %, or 40 wt % to 75 wt %, or 40 wt % to 60 wt %.
To deposit an amine-based sorbent on a support, the amine-based sorbent can be dissolved and/or dispersed in a solvent. In various aspects, the solvent can include water, methanol, ethanol, propanol, iso-propanol, propylene glycol (glycols), propylene glycol propyl ether (glycol ethers), hexane, toluene, and combinations thereof. One factor in selecting a solvent is the solubility of the polymer or other amine in the solvent, in order to obtain the highest dispersion possible on the support. Depending on the aspect, the solvent may be paraffinic, aromatic, and/or may contain functional groups such as hydroxyls or ether linkages. In some aspects, the solvent can have a boiling point of 200° C. or less, such as down to 50° C. To facilitate removing the solvent when loading an amine on a support, it can be beneficial for the solvent to be easily removed by simple evaporation, thermal evaporation, or by vacuum. Additionally or alternately, it can be beneficial to have a solvent that can solubilize the amine (such as a polymeric amine) at concentrations between 0.1 wt % to 75 wt % % of amine in the solvent, or 1.0 wt % to 50 wt %.
To illustrate depositing an amine on a support, an example procedure is provided using methanol as a solvent for depositing polyethylene imine (PEI). It is understood that other combinations of solvent and/or amine can similarly be used.
First, PEI was dissolved in methanol. The mixture of PEI and methanol was mixed until the PEI was dissolved/dispersed in the methanol to form a clear or substantially clear solution. Concentrations of PEI were dissolved ranging from 1.0 wt % to 50 wt % PEI relative to the total weight of the solution.
Based on the weight of PEI (or another amine) in solution, the amount of PEI for loading on the support (wt PEI on support) can be calculated. The calculations are based on the weight of the support material (wt support), the target weight percentage loading of PEI on the support material (wt % loading PEI), and the weight percentage of PEI relative to the weight of the solution (wt % PEI in solution). Based on these values, the amount of PEI that will be deposited on a support can be calculated as
The amount of solution used for the impregnation is calculated as
For example, impregnating 10 g of zeolite to a 60 wt % loading of PEI requires 10 g of material to be slurried in 100 g of a 15% solution of PEI in MeOH.
To impregnate a support, the desired amount of support material to be impregnated can be weighed out. The target amount of PEI solution is then added to the support material powder to form a slurry. The slurry is then mixed for 6 to 18 hours in a scaled vessel. After the mixing (i.e., after the completion of the impregnation), the solvent can be removed in any convenient manner, such as through room temperature evaporation, in a forced air oven set at a temperature near the boiling point of the solvent, or in a vacuum oven. After solvent removal, the resulting material should be dry to slightly wet. The resulting material can then be tested for CO2 capacity as measured by thermogravimetric analysis (TGA).
In some aspects, an amine sorbent supported on a support material could be used for sorption of CO2 by depositing the amine sorbent on particles of the support material. Such particles could then be used, for example, as a packed bed. However, passing a gas flow through a packed bed can tend to result in a noticeable pressure drop. One option for reducing or minimizing pressure drop while still providing the supported amine sorbent throughout a volume is to deposit the supported amine sorbent on a structural support that includes flow channels. A monolith is an example of a structural support. The flow channels of the monolith can provide a large surface area for contacting a gas flow with the supported amine sorbent by coating one or more surfaces within the flow channels with the supported amine sorbent. Because each individual cell provides surface area for deposition of the supported amine sorbent, including a large number of cells or channels per unit area can substantially increase the available surface area for the sorbent. Similarly, a large number of channels can facilitate higher volume flow rates while reducing or minimizing pressure drop. Such monoliths can generally be referred to as honeycomb monoliths. It is noted that the terms “cell” and “channel” can be used interchangeably to refer to the passages through a monolith.
The monolith can have any convenient shape suitable for use as a surface for receiving a supported amine sorbent and/or other bonding layers. The monoliths can be fabricated from any convenient material that can withstand the sorption environment while being substantially non-reactive in the presence of the gas flows. One option is to use a ceramic type monolith, such as a monolith composed of alumina or an alumina alloy. Additionally or alternately, a monolith can correspond to an extruded structure. A small reactor may include a single monolith, while a larger reactor can include a number of monoliths, while a still larger reactor may be substantially filled with an arrangement of many honeycomb monoliths. Each monolith may be formed by extruding monolith blocks with shaped (e.g., square, trigonal, or hexagonal) cross-section and two- or three-dimensionally stacking such blocks above, behind, and beside each other.
In some aspects, honeycomb monoliths can be characterized as having open frontal area (or geometric void volume) between 30% to 70%, or 30% to 60%, or 40% to 70%, or 40% to 60%, or 45% to 55%. Additionally or alternately, a monolith can have a conduit density between 50 to 900 cells per square inch (CPSI), or 50 to 600, or 300 to 900, or 300 to 600, or 350 to 550. This roughly corresponds to 7 to 140 cells per square centimeter, or 45 to 140, or 7 to 95, or 45 to 95, or 55 to 85. In some aspects, this type of cell density roughly corresponds to cells or channels that have a diameter/characteristic cell side length of only a few millimeters, such as on the order of roughly one millimeter.
In some aspects, any convenient type of amine-based sorbent can be supported on a support material as described herein. In other aspects, the sorbent material supported on the support can correspond to a modified polyamine sorbent material.
In various aspects, sorbent materials are provided with selectivity for sorption of CO2. The sorbent materials are formed by using a multi-dentate reagent to react with a relatively low molecular weight polyamine, such as a relatively low molecular weight polyethylencimine (PEI). This forms a new modified polymer material that can be supported on a support material to provide a supported sorbent material. The multi-dentate reagent can correspond to, for example, a di-epoxy, a tri-epoxy, or another multi-dentate reagent that would be expected to have cross-linking activity with a polyamine. The amount of the multi-dentate reagent can be low enough so that only a reduced or minimized number of the nitrogen atoms in the polyamine are reacted during the cross-linking. Other examples of multi-dentate ligands can include, but are not limited to, multi-functional aldehydes (either with or without reductive amination), multi-functional halides, multi-functional isocyanates, and ligands including combinations of epoxies, aldehydes, halides, and/or isocyanates. The resulting modified polymer material can maintain the desirable sorption capacity of a lower molecular weight polyamine while having reduced volatility and/or increased resistance to oxidation. The reduced volatility and/or increased resistance to oxidation can allow the resulting modified polymer material to maintain capacity for sorption for longer periods of time. Additionally, by using a reduced or minimized amount of the multi-dentate reagent, the reduced volatility and/or increased resistance to oxidation can be achieved while still substantially maintaining a high CO2 sorption capacity for the resulting supported modified polyamine material.
Selecting an amine-based material for sorption and desorption of CO2 typically involves balancing a variety of factors. One type of material that would be desirable for CO2 sorption/desorption is polyamines. A number of types of polyamine materials can be readily synthesized, providing a relatively low cost material with a high density of potential CO2 sorption sites. However, a number of challenges remain with implementing such polyamines.
Some challenges are related to sorption capacity. For example, polyamines that correspond to polymeric amines provide a repeating structure that includes a potential CO2 sorption site in each repeat unit, as the molecular weight of a polyamine increases, the sorption capacity of the polyamine tends to decrease. Thus, based on sorption capacity considerations, a lower molecular weight polyamine would be preferable.
Other challenges are related to stability of a polyamine sorbent system over an extended period. In order to increase availability of sorption sites, it is desirable to support a polyamine sorbent on a support with relatively high surface area. Examples of support materials can include high surface area refractory oxides (such as alumina) and/or zeotype supports. Unfortunately, as the molecular weight of a polyamine decreases, the volatility of the polyamine increases. Volatility is undesirable because it can lead to loss of polyamine from a support during normal operation, especially at the higher temperature parts of the process, which a sorbent is exposed to during the desorption step in a sorption/desorption cycle.
Additionally, polymers, especially polyamines, can also suffer from oxidation when exposed to oxygen. Many of the CO2-containing gases where CO2 removal is desirable can also contain oxygen, with the amount of oxygen possibly being substantially larger than the amount of CO2 (e.g., air). While degradation of a polymer due to the presence of oxygen can be reduced or minimized by controlling the temperature during exposure to oxygen, improved resistance to oxidation would be desirable to increase the run lengths for a sorbent system while maintaining a target sorption capacity.
It has been discovered that the benefits of using a lower molecular weight polyamine as a CO2 sorbent can be largely maintained while improving the resistance to oxidation and lowering the volatility. This combination of benefits is achieved by reacting the relatively low molecular weight polyamine with a bidentate (or polydentate) linking reagent in a reduced or minimized amount. In some aspects, the amount of multi-dentate linking reagent is selected so that 0.5 mol % to 30 mol % of the nitrogen atoms in the polyamine are reacted during cross-linking, or 1.0 mol % to 30 mol %, or 2.5 mol % to 30 mol %, or 5.0 mol % to 30 mol %, or 0.5 mol % to 15 mol %, or 1.0 mol % to 15 mol %, or 2.5 mol % to 15 mol %, or 5.0 mol % to 15 mol %, or 1.0 mol % to 9.0 mol %, or 2.5 mol % to 9.0 mol %, or 0.5 mol % to 7.5 mol %, or 1.0 mol % to 7.5 mol %, or 2.5 mol % to 7.5 mol %. It is noted that the amount of nitrogen that is reacted during cross-linking is roughly proportional to the amount of multi-dentate linking reagent. It is believed that the linking reagent can allow for linking between polyamine chains as well as linking within a single polyamine chain. The resulting modified polymer can substantially retain the sorption capacity of the lower molecular weight starting polymer material while having reduced volatility and increased resistance to oxidation. In addition to providing an unexpectedly improved combination of sorption capacity and oxidation resistance, the modified polymer material can also be formed in a relatively straightforward manner. In particular, the polyamine reagent does not need to be reacted or functionalized prior to reacting the polyamine with the linker. In various aspects, the low molecular weight polyamine can correspond to a polymer with an oxygen content of 1.0 wt % or less, or 0.1 wt % or less, such as down to having substantially no oxygen content. Additionally or alternately, the modified polymer material corresponds to a material that can be readily incorporated into/on a solid sorbent, such as a monolith or particles of a refractory oxide and/or zeolite. This can reduce or minimize the difficulties with attempting to build a commercial scale structure that incorporates the sorbent material. Supporting the polymer material can also allow a thin layer to be formed, which can assist with maintaining a higher porosity. This is in contrast to a self-supporting polymer, which typically has a lower porosity in order to maintain structural integrity.
In various aspects, a modified polymer composition can be formed by reacting a low molecular weight polymeric polyamine with a multi-dentate (such as bi-dentate or tri-dentate) linker compound. Formation of the modified polymer can be achieved in any convenient manner. For example, the polyamine can be dissolved in water, ethanol, and/or another suitable solvent to form a solution with a lower viscosity than the neat polyamine. The multi-dentate linker can then be added to the solution. The solution can be maintained at a reaction temperature, such as 0° C. to 50° C., for a reaction time of 0.1 hours to 10 hours, or 0.1 hours to 2.0 hours to form the modified polymer material. Optionally but preferably, the solution can be stirred or mixed during the reaction time. In some aspects, a support material can then be added to the solution containing the modified polymer material to impregnate the modified polymer on a support. The support material can be contacted with the modified polymer at a temperature of 20° C. to 75° C. for an impregnation time of 0.1 hours to 10 hours, or 0.1 hours to 2.0 hours to form a supported modified polyamine material. The impregnated support material can then be dried to remove the water.
For the low molecular weight polymeric polyamine, a variety of types of polyamine polymers can be suitable. Polyethyleneimine (PEI) is an example of a suitable polyamine. Other types of polyamine polymers (including polyimines) can also be used, such as polyhydroxylamine. Still other examples of polyamines include, but are not limited to, polyvinylamine, polypropyleneimine, polyallylamine, poly(2-dimethylaminoethyl acrylate), poly(2-dimethylaminoethyl methacrylate) and other vinyl polymers. In some aspects, the polyamine can correspond to a functionalized polyamine. Prior to reaction with the multi-dentate linker, the polyamine can correspond to a branched or a non-branched polymer chain.
Generally, the low molecular weight polyamine can have a weight average molecular weight of 500 Da (Daltons) to 15,000 Da, or 500 Da to 10,000 Da, or 500 Da to 5,000 Da, or 500 Da to 2,000 Da, or 500 Da to 1,500 Da. Additionally or alternately, the low molecular weight polyamine can have a number average molecular weight of 500 Da (Daltons) to 5,000 Da, or 500 Da to 2,500 Da, or 500 Da to 1,300 Da, or 500 Da to 1,000 Da. It is noted that for many types of polymers, there is a difference between the number average molecular weight and the weight average molecular weight (i.e., polydispersity).
Polydispersity is defined as the ratio of the weight average molecular weight divided by the number average molecular weight. In some aspects, the polydispersity for the polyamine can be 1.5 or less, or 1.4 or less, or 1.3 or less, such as down to 1.0 (i.e., having substantially no polydispersity).
The multi-dentate linker can correspond to a compound that includes functional groups that are suitable for functionalizing an amine. Examples of such compounds include di-epoxies, tri-epoxies, and di-aldehydes. 1,2,7,8 diepoxyoctane (DENO) is an example of a di-epoxy compound that can be used to form a modified polymer material.
In various aspects, the amount of multi-dentate linker in the synthesis solution for forming the modified polymer can correspond to 0.5 wt % to 33 wt % of the combined amount of low molecular weight polyamine and linker in the synthesis solution, or 0.5 wt % to 25 wt %, or 0.5 wt % to 15 wt %, or 0.5 wt % to 10 wt %, or 2.0 wt % to 33 wt %, or 2.0 wt % to 25 wt %, or 2.0 wt % to 15 wt %, or 2.0 wt % to 10 wt %, or 4.0 wt % to 33 wt %, or 4.0 wt % to 25 wt %, or 4.0 wt % to 20 wt %, or 4.0 wt % to 15 wt %, or 4.0 wt % to 10 wt %. Preferably, the amount of multi-dentate linker corresponds to 20 wt % or less of the combined amount of low molecular weight polymine and linker in the synthesis solution, or 15 wt % or less, or 10 wt % or less, such as down to 0.5 wt % or possibly still less. Using such a reduced or minimized amount of the multi-dentate linker can result in reaction of a corresponding reduced or minimized amount of nitrogen atoms in the polyamine, so that the stability benefits are achieved while retaining a high CO2 capacity in a supported amine material. It is noted that this is a weight percent relative to only the combined amount of polyamine and linker in the synthesis solution; any support material, solvent, and/or other components in the solution are not included in this relative weight percentage. This corresponds to a weight ratio of polyamine to linker in the synthesis solution of roughly 2.0 (i.e., 2.0:1) or more, or 4.0 or more, or 5.0 or more, or 15 or more, or 20 or more, such as up to 200 or possibly still more, or up to 250 or possibly still more. For a comparison on a molar basis, the weight of a monomer of the polyamine can be used as the basis for making a molar comparison with the linker. On a molar basis, the ratio of moles of polyamine monomer to moles of linker can be 5.0 to 1000, or 5.0 to 650, or 5.0 to 350, or 9.0 to 1000, or 9.0 to 650, or 9.0 to 350, or 18 to 1000, or 18 to 650, or 18 to 350, or 30 to 1000, or 30 to 650, or 30 to 350.
In various aspects, due to the nature of the modified polyamine material, the modified polyamine material can be used as a supported modified polyamine material when using the material for sorption/desorption of CO2. For such a supported modified polyamine material, using a reduced or minimized amount of the multi-dentate linker can result in a supported modified polyamine having an equilibrium CO2 capacity of 0.5 mmol CO2/g polyamine or higher at 35° C. in the presence of 100 kPa of CO2, or 1.5 mmol CO2/g polyamine or higher, or 2.3 mmol CO2/g polyamine or higher, or 2.5 mmol CO2/g polyamine or higher, or 2.7 mmol CO2/g polyamine or higher, or 3.0 mmol CO2/g polyamine or higher, such as up to 7.0 mmol CO2/g polyamine or possibly still higher. Additionally or alternately, in various aspects, the supported modified polyamine material can retain 60% or more of a maximum equilibrium CO2 capacity after exposure of the supported modified polyamine material to flowing air at 140° C. for 60 minutes in 10 minute intervals, or 65% or more, or 70% or more, or 75% or more, such as up to 85% or possibly still more.
After reacting the low molecular weight (polymeric) polyamine with the multi-dentate linker, the resulting modified polymer material can have an increased molecular weight. In some aspects, the modified polymer material can have a weight average molecular weight be between 1.5 times to 20 times the weight average molecular weight of the polyamine reagent, or 1.5 times to 10 times, or 3.0 times to 20 times. In aspects where the weight average molecular weight of the polyamine reagent is between 500 Da to 1500 Da, the resulting modified polymer material can have a weight average molecular weight of 750 Da to 20,000 Da, or 750 Da to 10,000 Da, or 1500 Da to 20,000 Da, or 1500 Da to 10,000 Da. In such aspects, the polydispersity of the resulting modified polymer material can be between 1.0 to 2.5, or 1.2 to 2.5, or 1.4 to 2.5, or 1.0 to 2.0, or 1.2 to 2.0, or 1.4 to 2.0, or 1.0 to 1.5.
The modified polymer material can also have an unexpectedly high sorption capacity for CO2 (and/or other potential sorption components) relative to the oxidation resistance of the modified polymer material. Conventionally, lower molecular weight polyamines have improved sorption capacity, but reduced oxidation resistance. It has been discovered that by forming a modified polymer material, the sorption capacity of the underlying low molecular weight polyamine can be substantially retained while providing improved resistance to oxidation. In various aspects, the modified polymer material can have an initial CO2 sorption capacity that corresponds to 70% or more of the initial sorption capacity of the polyamine reagent, or 80% or more, such as up to 100% or possibly still higher. This sorption capacity can be achieved while reducing or minimizing the loss of sorption capacity over time when the modified polymer material is exposed to the cyclic conditions encountered in a sorption/desorption process.
It is noted that in some aspects, the cross-linked material described herein has a reduced or minimized amount of pore volume (such as substantially no pore volume) unless it is supported on a support material. In such aspects, the cross-linked material described herein, as a self-supported material (such as in the form of particles), can have a pore volume of 25 m2/g or less, or 10 m2/g or less, such as down to substantially no pore volume.
In various aspects, a polyamine material, such as a modified polyamine material, optionally supported on a support material, can be used in a process for selectively sorbing a component from a fluid phase flow, and then desorbing the sorbed component to perform a cyclic sorption/desorption process. In some aspects, CO2 can be the component that is selectively sorbed and desorbed. In other aspects, any other convenient component which can undergo chemisorption and/or adsorption at amine sites can be the component that is selectively sorbed and desorbed.
An example of a component that can be sorbed/desorbed is CO2. One option for performing a CO2 sorption/desorption cycle is to use temperature to facilitate sorption and then desorption of the CO2. For example, a sorbent material can be exposed to CO2 at a lower temperature in order to sorb CO2, followed by increasing the temperature of the material to desorb the CO2.
In some aspects, sorption of CO2 can be performed by exposing the modified polymer material to CO2 at a temperature between 0° C. and 70° C., or 15° C. to 70° C., or 0° C. to 50° C., or 15° C. to 50° C. During sorption, the modified polymer is exposed to a fluid (typically gas phase) stream containing multiple components, with one of the components corresponding to CO2. The CO2 concentration in the fluid stream can vary widely depending on the application. In some aspects such as a direct air capture system, the CO2 concentration can be relatively low, such as a CO2 concentration of 100 vppm to 1000 vppm, or 100 vppm to 600 vppm. In other aspects, the fluid stream can have higher CO2 concentration, such as a CO2 concentration of 0.1 vol % to 10 vol %, or possibly still higher. The total pressure during the sorption step can range from 70 kPa-a to 10,000 kPa-a, or 70 kPa-a to 5,000 kPa-a, or 70 kPa-a to 1,000 kPa-a, or 100 kPa-a to 10,000 kPa-a, or 100 kPa-a to 5,000 kPa-a, or 100 kPa-a to 1,000 kPa-a.
After a sorption step, a different set of conditions can be used for desorption. In a temperature swing cycle, desorption can be facilitated by increasing the temperature of the sorbent environment. Optionally, the pressure can also be decreased. In some aspects, desorption of CO2 can be performed at a temperature of 70° C. to 200° C., or 70° C. to 170° C., or 70° C. to 140° C., or 90° C. to 200° C., or 90° C. to 170° C., or 90° C. to 140° C., or 110° C. to 200° C., or 110° C. to 170° C. Optionally, the temperature during desorption can be greater than the temperature during sorption by 30° C. or more, or 50° C. or more, such as up to 110° C. or possibly still more. The total pressure during the sorption step can range from 70 kPa-a to 10,000 kPa-a, or 70 kPa-a to 5,000 kPa-a, or 70 kPa-a to 1,000 kPa-a, or 100 kPa-a to 10,000 kPa-a, or 100 kPa-a to 5,000 kPa-a, or 100 kPa-a to 1,000 kPa-a. Optionally, the pressure during desorption can be similar to the pressure during sorption. Optionally, the pressure during desorption can be lower than the pressure during sorption by 20 kPa or more, or 50 kPa or more, or 100 kPa or more, such as up to 8000 kPa or possibly still more. In some aspects, a sweep fluid can be passed over and/or through the sorbent environment during desorption to assist with removing the desorbed CO2.
A series of support materials were prepared or acquired. Table 1 shows the materials, including several comparative examples. In Table 1, largest diffusing sphere refers to the largest diffusing sphere that can pass through the pore network of the material. The properties in Table 1 correspond to properties that are inherent to the crystalline framework structure.
Synthesis of EMM-57: The syntheses shown below are not the only ones that will work for this framework. More aluminous compositions can also tend to be effective. Examples of this zeolite are described in U.S. Pat. No. 10,807,875. An exemplary synthesis of EMM-57 is illustrated below but is not limiting. Variations in Si/Al2 of the final product, silica source, alumina source, and the addition of other cations to the synthesis can contribute to controlling the EMM-57 support acidity, morphology, crystal size, aggregate size, and agglomerate size. As a synthesis example, add 8587.0 g of 10 wt % 1,2,3-trimethyl-1H-benzo[d] imidazol-3-ium hydroxide to 5276.7 g of water. Add 38.2 g of dried aluminum hydroxide gel and 13.5 g of EMM-57 seeds to the hydroxide solution. Add 1084.4 g of precipitated silica to the aluminate solution and stir the mixture for 45 minutes to create a homogeneous slurry. Heat the slurry in a stirred autoclave for 60-96 hours at 170° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is EMM-57 with a SiO2/Al2O3 ratio of ˜70. The acid form of the crystalline support is made by heating the material in 5 volumes of flowing air/volume of catalyst while ramping at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
As the aluminum content of the EMM-57 is increased the PEI or PEI/DENO supported on the material is more uniformly dispersed on the support resulting in higher CO2 capacities with no change in adsorption or desorption kinetics. Add 852.4 g of 10 wt % 1,2,3-trimethyl-1H-benzo[d]imidazol-3-ium hydroxide to 374.9 g of water. Add 6.7 g of dried aluminum hydroxide gel and 1.3 g of EMM-57 seeds to the hydroxide solution. Add 98.6 g of precipitated silica to the aluminate solution. Stir the mixture for 45 minutes to create a homogenous slurry. Heat the mixture in a stirred autoclave for 240 hours at 170° C. and 288 hours at 180° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is EMM-57 with a SiO2/Al2O3 ratio of ˜40. The acid form of the crystalline support is made by heating the material in 5 volumes of flowing air/volume of catalyst while ramping at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
A more aluminous version can be made using the following procedure: Add 5.1 g of Sasol SIRAL 70 to 328.9 g of 10.2 wt % 1,2,3-trimethyl-1H-benzo[d]imidazol-3-ium hydroxide. Add 65.9 g of a 30 wt % silica colloidal suspension to the slurry. Stir the mixture for 45 minutes to create a homogenous slurry. Heat the mixture in a stirred autoclave for 240 hours at 170° C. and 288 hours at 180° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is EMM-57 with a SiO2/Al2O3 ratio of ˜30. The acid form of the crystalline support is made by heating the material in 5 volumes of flowing air/volume of catalyst while ramping at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
Synthesis of SFN framework zeotype: Add 0.69 g of 1 N NaOH and 4.23 g of a 9% solution of 1,2,3,5-tetramethyl-1H-benzo[d]imidazole-3-ium hydroxide to 0.05 g of water. Add 0.70 g of CBV-720 to the hydroxide solution with stirring. Stir the mixture for at least 10 minutes to create a homogeneous slurry. Heat the mixture in a rotating Teflon lined acid digestion vessel for 3 weeks at 160° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is the aluminosilicate version of SFN with a SiO2/Al2O3 ratio of ˜30. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 538° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst that is ramped at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
Synthesis of BEA framework zeotype: Add 36.7 g of 50 wt % NaOH and 428.7 g of 35 wt % TEA-OH to 545.8 g of water. Slowly add 225.6 g of 47% Al2 (SO4)3 solution and 7.3 g of beta seeds to the hydroxide solution. Add 175.9 g of precipitated silica to the aluminate solution and mix for 30 minutes to create a homogeneous mixture. Heat the mixture in a stirred autoclave for 168 hours at 170° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is beta with a SiO2/Al2O3 ratio of ˜15. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 550° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst that is ramped at ˜2° C./min to 550° C. Once at the proper temperature the material is held under flowing air for 4 hours.
Synthesis of MOR framework zeotype: Add 269.9 g of 10% NaOH to 681.8 g of water. Add 64.0 g of 43% sodium aluminate solution and 1.4 g of mordenite seed to the NaOH solution. Add 240.9 g of precipitated silica and 76.0 g of 50% TEA-Br solution to the sodium aluminate solution with stirring. Stir the mixture for at least 30 minutes to create a homogeneous slurry. Heat the mixture in a stirred autoclave for 48 hours at 138° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is EMM-34 with a SiO2/Al2O3 ratio of ˜20. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 538° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst that is ramped at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
Synthesis of MFI framework zeotype: Dissolve 3.66 g of NaOH in 2569.1 g of 20% tributylhexamethonium dihydroxide and 120.66 g of de-ionized water. While stirring, add 24.79 g of dried aluminum hydroxide gel and 481.8 g of precipitated silica to the hydroxide solution. Stir the mixture for 30 minutes. Evaporate the water from the mixture using flowing nitrogen while under agitation. Evaporate until the weight of the mixture is 1500 g. If the material is dry enough, grind the powder to a fine consistency to help homogenize the powder. If the weight is below the desired 1500 g add water to reach the final desired weight. Add the mixture to a 2-liter acid digestion vessel. Heat to 115° C. for 168 hours followed by 168 hours at 135° C. while rotating the digestion vessel at 10 rpm. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is EMM-20 with a SiO2/Al2O3 ratio of ˜55. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 538° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst while ramping at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
Synthesis of MEL framework zeotype: Mix 1854 g of water with 5416 g of concentrated TBA-OH [2.78 mmole/g OH—]. While agitating the TBA-OH solution, slowly add 1266 g of 47% aluminum sulfate solution to the hydroxide solution. Add 59 g of ZSM-5 seed to the TBA aluminate solution. Slowly add 250.9 g of precipitated silica to the aluminate solution. Add the mixture to a horizontal plough shear mixer. Heat the mixture to 135° C. for 279 hours while mixing at 20 rpm. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is EMM-30 with a SiO2/Al2O3 ratio of ˜45. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 538° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst while ramping at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
Synthesis of ZSM-57: Add 450.3 g of 5% NaOH to 598.7 g of water. Add 17.7 g of 45% sodium aluminate solution and 1.7 g of ZSM-57 seed to the NaOH solution. Add 147.1 g of precipitated silica, 95.8 g of a 25% solution of diquat-5 dibromide, and 22.8 g of 50% TEA-Br solution to the sodium aluminate solution with stirring. Stir the mixture for at least 30 minutes to create a homogeneous slurry. Heat the mixture in a stirred autoclave for 90 hours at 160° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is ZSM-57 with a SiO2/Al2O3 ratio of ˜40. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 538° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst that is ramped at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
Synthesis of ZSM-23: Add 15.8 g of 50% NaOH to 1051.5 g of water. Add 17.95 g of 47% Al2(SO4)3 solution and 6.2 g of ZSM-23 seed to the NaOH solution. Add 179.0 g of precipitated silica and 63.4 g of pyrrolidine to the sodium aluminate solution with stirring. Stir the mixture for at least 30 minutes to create a homogeneous slurry. Heat the mixture in a stirred autoclave for 24 hours at 160° C. Isolate the crystal via vacuum filtration, wash with 2 volumes of water, and dry the filter cake. The powder XRD of the resulting product is ZSM-23 with a SiO2/Al2O3 ratio of ˜100. The acid form of the crystalline support is prepared by calcining the material in nitrogen at 538° C., exchanging three times with ammonium nitrate, and heating the material in 5 volumes of flowing air/volume of catalyst while ramping at ˜2° C./min to 538° C. Once at the proper temperature the material is held under flowing air for 6 hours.
PEI was deposited on the support materials shown in
To determine CO2 capacity via TGA, samples were first exposed to a purge procedure. The samples were initially ramped to 110° C. at roughly 10° C. per minute under 1 atm (˜100 kPa-a) of nitrogen. The samples were held at 110° C. for roughly 4 hours. The samples were then cooled under nitrogen at roughly 10° C. per minute to reach a temperature of 35° C. The samples were held at 35° C. under the nitrogen for roughly 30 minutes. The gas phase environment was then replaced with 1 atm (˜100 kPa-a) of CO2. The samples were held at 35° C. under the CO2 for roughly 3 hours. The weight of the sample was monitored using the TGA device during these steps to characterize the CO2 capacity.
As shown in
Additional characterization can be used to further understand the relationship between various properties of the support material and the capacity of the supported polyethylene imine.
As shown in
As shown in
In the following examples, two types of supported amine-based polymers are tested for CO2 sorption/desorption properties, volatility, and oxidative stability.
One type of supported polymer system (Comparative Example A) corresponds to polyethyleneimine (PEI) supported on a particulate support material. Materials corresponding to Comparative Example A were formed by diluting PEI in either water or ethanol to make a low viscosity solution. A powder of high surface area support material was then added to the solution and mixed at 50° C. for 24 hrs, followed by drying under nitrogen atmosphere to produce Comparative Example A.
The other type of supported polymer system (Example B) corresponded to a modified polymer material impregnated on the same type of support. Materials corresponding to Sample B were formed by diluting PEI in ethanol to make a low viscosity solution. Next, 1,2,7,8 diepoxyoctane (DENO) was added to the PEI/EtOH solution at ambient temperature (roughly 20° C.) and stirred for 30 minutes. Over this time, the DENO and the PEI reacted to form a modified polymer material with higher molecular weight. After 30 minutes, the powder of high surface area support material was added to the solution and mixed at 50° C. for 24 hrs, followed by drying under nitrogen atmosphere to produce Sample B.
The two types of materials were tested for CO2 capacity. Table 2 shows the relative amounts of PEI, support, and DENO (if any) that were used to make the various samples. Table 2 also shows the amount of CO2 uptake in millimoles of CO2 per gram of either PEI or PEI plus support. It is noted that for the samples including DENO, the DENO is not included in the calculation of CO2 capacity when using units of mmol/g PEI.
The CO2 capacity values were determined by thermogravimetric analysis (TGA). To determine CO2 capacity, samples were first exposed to a purge procedure. The samples were initially ramped to 110° C. at roughly 10° C. per minute under 1 atm (˜100 kPa-a) of nitrogen. The samples were held at 110° C. for roughly 4 hours. The samples were then cooled under nitrogen at roughly 10° C. per minute to reach a temperature of 35° C. The samples were held at 35° C. under the nitrogen for roughly 30 minutes. The gas phase environment was then replaced with 1 atm (˜100 kPa-a) of CO2. The samples were held at 35° C. under the CO2 for roughly 3 hours. The weight of the sample was monitored using the TGA device during these steps in order to characterize the CO2 capacity.
As shown in Table 2, addition of low levels of DENO to form a modified polymer material results in a modified polymer material with comparable levels of CO2 capacity to the unmodified PEI. Thus, the modified polymer material had similar CO2 capacity to unmodified PEI at weight ratios of PEI to DENO of roughly 10 or more (molar ratio of PEI monomer units to DENO of roughly 30 or more, as defined herein). At lower ratios of PEI to DENO (weight ratio less than 9.0, molar ratio less than roughly 30), however, the CO2 capacity started to drop. This drop becomes more pronounced at weight ratios of PEI to DENO lower than 4.0 (molar ratio less than roughly 13).
Differential thermal analysis (DTA) was used to characterize the volatility and oxidative stability of the various samples. The DTA was performed in the same apparatus used for the TGA analysis in Example 3. To investigate volatility, samples corresponding to Examples A2, B1, B2, B3, and B4 were each ramped to 140° C. at a rate of 5° C. per minute under nitrogen. The samples were then held at 140° C. for roughly 4 hours to measure the mass loss (volatility) due to exposure to 140° C. for an extended period. At the end of the roughly 4 hours, the gas phase environment for the samples was switched to air. The samples were then held at 140° C. for roughly another 4 hours to determine mass loss due to formation of volatile compounds via oxidation.
As shown in
It is noted that the reduced volatility benefits shown in
To further illustrate the benefits of the modified polymer materials with regard to improving material lifetime (e.g., slowing down oxidative degradation that retards CO2 adsorption), cyclical oxidation/CO2 uptake tests were performed. In this example, the CO2 capacity of a sample corresponding to Example A1 was compared with a sample corresponding to Example B2 after cyclic exposure to air at temperatures of either 120° C. or 140° C.
The cyclic process was performed using the TGA unit. The cyclic process of oxidation, CO2 sorption, and CO2 desorption was performed as follows. First, to prepare a sample, the sample was ramped at 10° C./min to 140° C. under N2. The sample was then held at 140° C. for roughly 180 minutes under N2 to desorb any CO2 or H2O. The sample was then cooled at 10° C./min to 35° C. After reaching 35° C., the gas phase environment was switched to CO2. The temperature was maintained at 35° C. in the presence of the CO2 for roughly 30 minutes to measure a baseline CO2 capacity. The gas phase environment was then purged with N2.
At this point, the cyclic process was started. First, the temperature of the sample was ramped to either 120° C. or 140° C. at 10° C./min under the N2 gas phase environment. The gas phase environment was then switched to air. The temperature of either 120° C. or 140° C. was maintained for roughly 10 minutes in the presence of the air gas phase environment. The gas phase environment was then purged with N2. Next, the temperature was ramped down to 35° C. at 10° C./min. The gas phase environment was then switched to CO2, and the sample was held at 35° C. for roughly 30 minutes in the presence of the CO2 gas phase environment to measure a new CO2 capacity. The process was then repeated to measure how cyclic oxidation impacted CO2 capacity over time.
An additional unexpected finding was that using relatively low amounts of a linking agent to form a modified polymer resulted in a modified polymer that had sorption kinetics that were comparable to the unmodified polymer. This was determined based on additional characterization of the samples described in Table 2. This additional characterization corresponded to “breakthrough” characterization.
For this additional characterization, all samples were sieved to 425-250 microns. The samples were then packed into a column and heated under a flow of 100 sccm N2 to 100° C. for 16 hours. The samples were then placed on a breakthrough test unit with high-speed switching valves. A stream of 8333 ppm CO2 in N2 was delivered to the packed bed maintained at 30° C. in a furnace. The effluent gas stream was measured via mass spectrometry (see
As shown in
The types of amines present in the unmodified and modified PEI samples were characterized using nuclear magnetic resonance (NMR) spectroscopy.
By using NMR quantification, the percentage of amines in a polyamine sample that participate in cross-linking can be quantified. This procedure is described in an article by Choi et al., (Nat. Commun. 7:12640 doi: 10.1038/ncomms12640 (2016)). Briefly, a sample of the polyamine prior to reaction (such as unmodified PEI) can be characterized using 13C-NMR to characterize the number of primary, secondary, and tertiary amines in the sample. A sample after cross-linking (such as modified PEI) can then be characterized in a similar manner. By characterizing the change in the number of primary, secondary, and tertiary amines before and after modification, the degree of cross-linking can be determined.
It has been discovered that the benefits of cross-linking the polyamine can be achieved at a relatively low level of cross-linking. By performing a reduced or minimized amount of cross-linking, the unexpected combination of increasing stability while preserving CO2 capacity can be achieved.
A series of supported amines were prepared by forming cross-linked polyethyleneimine (PEI) on EMM-57. The cross-linking agent was 1,2,7,8-diepoxyoctane (DENO). Table 3 shows characterization of the cross-linked PEI, including the relative amounts of PEI, EMM-57, and DENO used to form the supported cross-linked amine composition and the resulting CO2 capacities.
As shown in Table 3, the percentage of N atoms reacted in the PEI increases roughly linearly with the amount of cross-linking agent. When the percentage of N atoms in the polyamine that are reacted during cross-linking is greater than 9.0 mol %, the CO2 capacity of the resulting supported amine drops dramatically. increasing the amount of DENO relative to the amount of PEI (or other amine) results in an increase in the percentage of nitrogens in the PEI that are reacted. Table 4 shows characterization of additional supported amine samples based on PEI, EMM-57, and optionally DENO as a cross-linking agent.
In Table 4, all of the samples include roughly the same amount of PEI supported on roughly the same amount of EMM-57. The only difference is that some samples are cross-linked with various amounts of DENO. As shown in Table 3, the PEI samples without cross-linker have an average CO2 capacity of 3.6 mmol CO2/g PEI. When less than 7.6 wt % of DENO is included as a cross-linker, the CO2 capacity remains above 2.8 mmol CO2/g PEI. However, further increases in the amount of PEI result in a sharp drop in CO2 capacity.
In Table 5, oxidation experiments were conducted where CO2 was first adsorbed at 35° C. (0 min in Table 5), then nitrogen was passed over the sample while heating to 140° C., followed by air flow for 10 minutes. This was repeated 6 times to give 60 total minutes of air oxidation at 140° C., where CO2 capacity was measured after each 10 minute oxidation step. Table 5 shows the results, where normalized CO2 capacity is listed at 20 minute intervals.
Embodiment 1. A supported amine sorbent, comprising: a support material comprising silica and alumina, the support material being crystalline, the support material comprising a pore volume of 0.20 g/cm3 or more, a ratio of mesopore volume to micropore volume of 1.0 or more, a total surface area of 100 m2/g or more, a ratio of Si to Al2 of 10-1000, and an acidity as measured by temperature programmed ammonia desorption of 0.10 meq/g or more; and 30 wt % to 80 wt % of a polyamine supported on the support material, relative to a weight of the support material.
Embodiment 2. A supported amine sorbent, comprising: a support material comprising silica and alumina, the support material comprising a pore volume of 0.20 g/cm3 or more, a ratio of mesopore volume to micropore volume of 1.0 or more, a total surface area of 100 m2/g or more, a ratio of Si to Al2 of 50-1000, and an acidity as measured by temperature programmed ammonia desorption of 0.10 meq/g or more; and 30 wt % to 80 wt % of a polyamine supported on the support material, relative to a weight of the support material.
Embodiment 3. The supported amine sorbent of any of the above embodiments, wherein the support material comprises a ratio of external surface area to total surface area of 0.15 or more.
Embodiment 4. The supported amine sorbent of any of the above embodiments, wherein the support material comprises a zeotype framework structure, or wherein the support material comprises a clay, or wherein the support material comprises a zeolitic material, or a combination thereof.
Embodiment 5. The supported amine sorbent of Embodiment 4, wherein the support material comprises a hierarchical zeotype structure.
Embodiment 6. The supported amine sorbent of Embodiment 4 or 5, wherein the support material comprises a zeotype framework structure selected from the group consisting of DON, SFN, MOR, MFI, MEL, BEA, MTW, MTT, and MFS.
Embodiment 7. The supported amine sorbent of any of Embodiments 4 to 6, wherein the support material comprises a zeotype framework structure selected from the group consisting of EMM-57, EMM-72, EMM-20, EMM-30, EMM-34, ZSM-5, ZSM-11, zeolite Beta, mordenite, ZSM-12, ZSM-5, ZSM-11, ZSM-23, and ZSM-57.
Embodiment 8. The supported amine sorbent of any of Embodiments 4 to 7, wherein the zeotype framework structure further comprises oxides of one or more of gallium, germanium, boron, zinc, and phosphorus.
Embodiment 9. The supported amine sorbent of any of the above embodiments, wherein the support material comprises a total surface area of 200 m2/g or more.
Embodiment 10. The supported amine sorbent of any of the above embodiments, wherein the support material comprises an acidity of 0.15 meq/g or more.
Embodiment 11. The supported amine sorbent of any of the above embodiments, wherein the support material comprises an average pore diameter between 2.0 nm and 50 nm.
Embodiment 12. The supported amine sorbent of any of the above embodiments, wherein the polyamine comprises polyethylene imine, polypropylene imine, polyhydroxylamine, a functionalized polyamine or a combination thereof.
Embodiment 13. The supported amine sorbent of any of the above embodiments, wherein the polyamine comprises a crosslinked polymeric amine, or wherein the polyamine comprises a branched polyamine, or a combination thereof.
14. The supported amine sorbent of any of the above embodiments, wherein the polyamine comprises a number average molecular weight of 200 Da to 100,000 Da.
Embodiment 15. The supported amine sorbent of any of the above embodiments, wherein the polyamine comprises a number average molecular weight of 200 Da to 2000 Da.
Embodiment 16. The supported amine sorbent of any of the above embodiments, further comprising a monolith, the supported amine sorbent being supported on one or more surfaces of the monolith.
While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.
This Non-Provisional Patent application claims priority to U.S. Provisional Patent Application No. 63/516,030, filed Jul. 27, 2023, and titled “Polyamine Sorbents On High Pore Volume Supports”. This application also claims priority to U.S. Provisional Patent Application No. 63/516,023 filed on Jul. 27, 2023, U.S. Provisional Patent Application No. 63/516,020 filed on Jul. 27, 2023, and U.S. Provisional Patent Application No. 63/568,661 filed on Mar. 22, 2024. The entire contents of each of the above documents is hereby incorporated by reference into the present application.
| Number | Date | Country | |
|---|---|---|---|
| 63516030 | Jul 2023 | US | |
| 63516020 | Jul 2023 | US | |
| 63516023 | Jul 2023 | US | |
| 63568661 | Mar 2024 | US |
