Patent Application
20250121354
Amine-functionalized aerogel compositions are provided that are capable of sorption and desorption of acid gas components.
Porous inorganic solids have found great utility as catalysts and separation media for industrial application. In particular, mesoporous materials, such as silicas and aluminas, having a periodic arrangement of mesopores are attractive materials for use in adsorption, separation and catalysis processes due to their uniform and tunable pores, high surface areas and large pore volumes. The pore structure of such mesoporous materials is large enough to absorb large molecules and the pore wall structure can be as thin as about 1 nm. Further, such mesoporous materials are known to have large specific surface areas (e.g., 1000 m2/g) and large pore volumes (e.g., 1 cm3/g). For these reasons, such mesoporous materials enable reactive catalysts, adsorbents composed of a functional organic compound, and other molecules to rapidly diffuse into the pores and therefore, can be advantageous over zeolites, which have smaller pore sizes. Consequently, such mesoporous materials can be useful not only for catalysis of high-speed catalytic reactions, but also as large capacity adsorbents.
It was further discovered that the inclusion of some organic groups in the mesoporous framework can provide adjustable reactive surfaces and also contributes to uniformity in pore size, higher mechanical strength, and hydrothermal stability of the material. Thus, mesoporous organosilica materials can exhibit unique properties compared to mesoporous silica such as enhanced hydrothermal stability, chemical stability, and mechanical properties. Organic groups can be incorporated using bridged silsesquioxane precursors of the form Si—R—Si to form mesoporous organosilicas.
Mesoporous organosilicas are conventionally formed by the self-assembly of the silsequioxane precursor in the presence of a structure directing agent, a porogen and/or a framework element. The precursor is hydrolysable and condenses around the structure directing agent. These materials have been referred to as Periodic Mesoporous Organosilicates (PMOs), due to the presence of periodic arrays of parallel aligned mesoscale channels. For example, Landskron, K., et al. [Science, 302:266-269 (2003)] report the self-assembly of 1,3,5-tris[diethoxysila]cylcohexane [(EtO)2SiCH2]3 in the presence of a base and the structure directing agent, cetyltrimethylammonium bromide to form PMOs that are bridged organosilicas with a periodic mesoporous framework, which consist of SiO3R or SiO2R2 building blocks, where R is a bridging organic group. In PMOs, the organic groups can be homogenously distributed in the pore walls. U.S. Pat. Pub. No. 2012/0059181 reports the preparation of a crystalline hybrid organic-inorganic silicate formed from 1,1,3,3,5,5 hexaethoxy-1,3,5 trisilyl cyclohexane in the presence of NaAlO2 and base. U.S. Patent Application Publication No. 2007/003492 reports preparation of a composition formed from 1,1,3,3,5,5 hexaethoxy-1,3,5 trisilyl cyclohexane in the presence of propylene glycol monomethyl ether.
However, the use of a structure directing agent, such as a surfactant, in the preparation of an organosilica material, such as a PMO, requires a complicated, energy intensive process to eliminate the structure directing agent at the end of the preparation process. This limits the ability to scale-up the process for industrial applications. Therefore, there is a need to provide additional organosilica materials with a desirable pore diameter, pore volume and surface area. Further, there is a need to provide such organosilica materials that can be prepared by a method that can be practiced in the absence of a structure directing agent, a porogen or surfactant.
U.S. Pat. No. 10,207,249 describes organosilica materials and uses thereof.
In an aspect, an organosilica material is provided that comprises a polymer of at least one monomer of Formula (I),
In various aspects, Z1, Z2, Z3, Z4, Z5, and Z6 each independently represent a hydrogen atom, a C1-C4 alkyl group, a bond to a silicon atom of another monomer of Formula (I), a bond to an aminosilyl group, a bond to a silicon atom that is bonded to three alkoxy groups, or a bond to a silicon atom of a secondary monomer comprising an acyclic alkoxy silane, wherein R11, R12, R13, R14, R15, and R16 each independently represent a hydrogen atom or a C1-C4 alkyl group, and wherein the organosilica material comprises a nitrogen content of 4.0 wt % to 9.5 wt %, a surface area of 300 m2/g or more, a pore volume of 0.75 cm3/g or more.
In various aspects, compositions corresponding to amine-functionalized organosilica materials are provided, along with methods of making such materials and methods of using such materials. The amine-functionalized organosilica materials are formed in part by using a single step synthesis process based on condensation of an alkoxy-substituted cyclic organosilane precursor in the presence of an aminosilane precursor so that an amine-functionalized polymer is formed. An acyclic alkoxy silane compound can also be used during the condensation to provide a secondary monomer that facilitates formation of the gel. The amine-functionalized organosilica materials are also formed in part by using at least one of a supercritical drying process and a freeze drying process. By using a supercritical drying process and/or a freeze drying process, an amine-functionalized organosilica material can be formed that has improved properties for sorption of CO2. In particular, the amount of nitrogen that can be incorporated into the amine-functionalized organosilica materials while still increasing the CO2 sorption capacity can be substantially increased.
Conventionally, use of amine silicas for carbon capture is known. The two most common methods used for forming an amine silica are a) impregnation of dissolved polyamines (such as polyethyleneimine or tetraethylenepentamine) into the porous support, and b) surface grafting of various aminosilane reagents (X3Si(CH2)nNH2, X3Si(CH2)3NHCH2CH2NH2, etc. where X=halide or alkoxy; n=1-11) by reaction with exposed hydroxyl groups on a pre-formed support surface. A variation on the impregnated polyamine approach is the impregnation of a small amine precursor monomer that polymerizes within the pores of the support to generate the polyamine. Whereas the impregnated polyamine is prone to leaching during repetitive temperature swing processing using a steam strip, the in-situ polymerization creates a larger polyamine that is unable to easily diffuse out.
Conventionally, the organosilicas used for forming an amine silica are typically formed by a two-step condensation process to form a gel, followed by drying of the resulting gel. For such conventional synthesis, the two steps during gel formation are required in order to allow for a swing in pH conditions from basic to acidic during the gel condensation. Such processes also typically require use of a surfactant, which adds to the costs associated with production of the organosilica.
As an alternative to the above methods, another option for forming an amine silica is solgel condensation of a cyclic organosilane precursor in the presence of an aminosilane precursor. The product of this condensation would be expected to possess anchored amine functional groups distributed uniformly on both external surface and within the bulk of the network structure. In various aspects, amine-functionalized organosilicas are provided based on condensation of an alkoxy-substituted cyclic organosilane in the presence of an aminosilane precursor. The condensation method involves forming an intermediate gel based on a monomer corresponding to a cyclic organosilane having a ring size of a six-membered ring or larger, such as a trisilacyclohexane, combined with an aminosilane precursor, such as for example, N-(aminoethyl)aminopropyl trialkoxysilane (TDA). The resulting intermediate gel is then dried via freeze-drying and/or using supercritical CO2 to form the polymer corresponding to the organosilica material. The synthesis described herein provides at least two unexpected benefits for the resulting amine-functionalized organosilica. First, the amine-functionalized organosilica is formed by a single-step method without the use of a templating agent. This simplifies synthesis and reduces costs associated with the synthesis. Additionally, by using supercritical CO2 and/or freeze-drying as the drying step(s) to form the resulting gel, improved CO2 sorption capacity can be achieved relative to the amine loading of the organosilica. This improved CO2 sorption capacity can be achieved for organosilica materials with elevated nitrogen contents, such as organosilica materials with nitrogen content of 4.0 wt % nitrogen or more.
The organosilica material can correspond to a polymer that includes monomer units corresponding to the monomer unit in
It is noted that the aminosilane precursors are incorporated into the polymer as terminal groups, and do not form part of the continuous polymer network. Therefore, the aminosilane precursors and/or functional groups derived therefrom are not referred to herein as monomers. However, in some aspects, alkoxy-substituted acyclic silanes, such as alkoxy-substituted acyclic aminosilanes, may also be present in the condensation mixture and may contribute secondary monomers that also form part of the polymer network. Such alkoxy-substituted acyclic silanes (including alkoxy-substituted acyclic aminosilanes) that serve as precursors for secondary monomers in the polymer are defined herein as gelator compounds.
In various aspects, the nitrogen content of the resulting organosilica materials can be 4.0 wt % to 9.5 wt %, relative to the weight of the organosilica material, or 4.0 wt % to 8.3 wt %, or 4.5 wt % to 9.5 wt %, or 4.5 wt % to 8.3 wt %, or 5.5 wt % to 9.5 wt %, or 5.5 wt % to 8.3 wt %, or 6.5 wt % to 9.5 wt %, or 6.5 wt % to 8.3 wt %.
It is noted that the use of supercritical CO2 drying for the production of high surface area, high porosity and low density silica aerogels is known conventionally. Conventionally, using supercritical CO2 for drying of conventional aerogels is reported to provide high gas diffusion rates in these materials relative to conventional silica substrates. Supercritical CO2 drying has also been found to reduce mass transfer resistance in amine-functionalized organosilica formed by conventional two-step synthesis methods.
For purposes of this invention and the claims hereto, the numbering scheme for the Periodic Table Groups is according to the IUPAC Periodic Table of Elements.
The terms “substituent”, “radical”, “group”, and “moiety” may be used interchangeably.
As used herein, and unless otherwise specified, the term “Cn” means hydrocarbon(s) having n carbon atom(s) per molecule, wherein n is a positive integer.
As used herein, and unless otherwise specified, the term “hydrocarbon” means a class of compounds containing hydrogen bound to carbon, and encompasses (i) saturated hydrocarbon compounds, (ii) unsaturated hydrocarbon compounds, and (iii) mixtures of hydrocarbon compounds (saturated and/or unsaturated), including mixtures of hydrocarbon compounds having different values of n.
A hydrocarbonaceous compounds refers to an organic compound that differs from a hydrocarbon in that one or more atoms different from carbon or hydrogen are present in the compound.
As used herein, and unless otherwise specified, an acyclic compound, group, or substituent refers to a compound, group, or substituent that does not include a ring structure.
As used herein, and unless otherwise specified, the term “alkyl” refers to a saturated hydrocarbon radical having from 1 to 12 carbon atoms (i.e. C1-C12 alkyl), particularly from 1 to 8 carbon atoms (i.e. C1-C8 alkyl), particularly from 1 to 6 carbon atoms (i.e. C1-C6 alkyl), and particularly from 1 to 4 carbon atoms (i.e. C1-C4 alkyl). Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, and so forth. The alkyl group may be linear, branched or cyclic. “Alkyl” is intended to embrace all structural isomeric forms of an alkyl group. For example, as used herein, propyl encompasses both n-propyl and isopropyl; butyl encompasses n-butyl, sec-butyl, isobutyl and tert-butyl and so forth. As used herein, “C1 alkyl” refers to methyl (—CH3), “C2 alkyl” refers to ethyl (—CH2CH3), “C3 alkyl” refers to propyl (—CH2CH2CH3) and “C4 alkyl” refers to butyl (e.g. —CH2CH2CH2CH3, —(CH3)CHCH2CH3, —CH2CH(CH3)2, etc.). As used herein, and unless otherwise specified, the term “alkylene” refers to a divalent alkyl moiety containing 1 to 12 carbon atoms (i.e. C1-C12 alkylene) in length and meaning the alkylene moiety is attached to the rest of the molecule at both ends of the alkyl unit. For example, alkylenes include, but are not limited to, —CH2—, —CH2CH2—, —CH(CH3)CH2—, —CH2CH2CH2—, etc. The alkylene group may be linear or branched.
As used herein, and unless otherwise specified, an aminosilyl group refers to a hydrocarbonaceous radical that includes at least one silicon atom and at least one nitrogen atom that corresponds to an amine nitrogen, with an alkyl group between the at least one silicon atom and the at least one nitrogen atom.
As used herein, and unless otherwise specified, the term “alkoxy” refers to —O-alkyl containing from 1 to about 10 carbon atoms. The alkoxy may be straight-chain or branched-chain. Non-limiting examples include methoxy, ethoxy, propoxy, butoxy, isobutoxy, tert-butoxy, pentoxy, and hexoxy. “C1 alkoxy” refers to methoxy, “C2 alkoxy” refers to ethoxy, “C3 alkoxy” refers to propoxy and “C4 alkoxy” refers to butoxy. Further, as used herein, “OMe” refers to methoxy and “OEt” refers to ethoxy.
As used herein, the term “hydroxyl” refers to an —OH group.
As used herein, the term “mesoporous” refers to solid materials having pores that have a diameter within the range of from about 2 nm to about 50 nm.
As used herein, the term “organosilica” refers to an organosiloxane compound that comprises one or more organic groups bound to two or more Si atoms.
As used herein, the term “silanol” refers to a Si—OH group.
As used herein, the term “silanol content” refers to the percent of the Si—OH groups in a compound and can be calculated by standard methods, such as NMR.
As used herein, the terms “structure directing agent,” “SDA,” and/or “porogen” refer to one or more compounds added to the synthesis media to aid in and/or guide the polymerization and/or polycondensing and/or organization of the building blocks that form the organosilica material framework. Further, a “porogen” is understood to be a compound capable of forming voids or pores in the resultant organosilica material framework. As used herein, the term “structure directing agent” encompasses and is synonymous and interchangeable with the terms “templating agent” and “template.”
As used herein, and unless otherwise specified, the term “adsorption” includes physisorption, chemisorption, and condensation onto a solid material and combinations thereof.
In this discussion, the ring structure corresponds to the atoms that form the cyclic structure. The members of a ring structure can be identified as the atoms that form a continuous loop without having to trace a path through an atom more than once. For example, in cyclohexane, all of the carbon atoms are part of the ring structure, but none of the hydrogen atoms are part of the ring structure. As another example, in the compound shown in
The invention relates to organosilica materials. Conventionally, organosilica materials are typically made by forming a polymer from one or more types of organosilica monomers. A templating agent is added to the mixture to induce formation of an organosilica gel that can then be dried to form the polymeric organosilica material. Due in part to the need to vary the pH in order to complete formation of the gel, this type of conventional synthesis route involves a two-step process, followed by drying of the resulting gel.
By contrast, in various aspects, an organosilica material can be formed via a one-step synthesis process, followed by drying of the resulting gel using supercritical CO2 and/or freeze-drying. The precursors for the one-step synthesis process include an alkoxy-substituted cyclic organosilane, an aminosilane precursor, and a gelator or gelling agent.
The alkoxy-substituted cyclic organosilane is the primary component for forming the organosilica material. An example of an alkoxy-substituted cyclic organosilane is an alkoxy-substituted silacyclohexane, such as hexa-ethoxy trisilacyclohexane. In this discussion, hexa-ethoxy trisilacyclohexane may be referred to as “3R”.
It is noted that in some aspects, instead of using only an alkoxy-substituted cyclic organosilane, a mixture of an alkoxy-substituted cyclic organosilane, such hexa-ethoxy trisilacyclohexane, and an alkoxy-substituted siloxy-substituted cyclic organosilane can be used. An example of an alkoxy-substituted siloxy-substituted cyclic organosilane is an alkoxy-substituted, mono-siloxy-substituted cyclic organosilane, such as penta-ethoxy mono-(triethoxy)siloxy-trisilacyclohexane (i.e., for one silicon position in the ring, the ethoxy group is replaced with a siloxy group). An example of penta-ethoxy mono-(triethoxy)siloxy-trisilacyclohexane is shown in
In various aspects, the alkoxy-substituted cyclic organosilane can include 3 or more silicon atoms in the ring structure. Optionally, the ring structure can correspond to a 6-membered ring. Optionally, the ring structure can include between 5 to 10 atoms that are part of the cyclic ring structure. Optionally, the ring structure can correspond to a single ring. For the carbons in the ring structure, one option is for the ring carbons to have two hydrogen substituents. In other aspects, one or more of the carbons in the ring structure can have a C1-C4 substituent. Larger alkyl groups could be possible, so long as steric hindrance from the alkyl groups does not prevent gel formation. For the alkoxy groups attached to the silicon atoms, the alkoxy groups can contain 1 to 6 carbons, or 2 to 6 carbons, or 1 to 4 carbons, or 2 to 4 carbons. In some aspects, the alkoxy groups attached to the silicon atoms in a single ring can each have the same number of carbon atoms (e.g., all alkoxy groups are methoxy, or all alkoxy groups are ethoxy).
The aminosilane precursor provides the amine-functionalization for the organosilica. Examples of aminosilane precursors that can be used in synthesis of amine-functionalized organosilicas are N-(aminoalkyl)aminoalkyl polyalkoxysilanes. In some aspects, the N-(aminoalkyl)aminoalkyl polyalkoxysilane can correspond to a trialkoxysilane. An example of an N-(aminoalkyl)aminoalkyl trialkoxysilane is N-(aminoethyl)aminopropyl trialkoxysilane, shown in
In various aspects, each of the aminoalkyl groups in the aminosilane precursor can correspond to a C1-C6 aminoalkyl. Optionally, each of the aminoalkyl groups can have the same chain length. Optionally, the N-(aminoalkyl)aminoalkyl alkoxysilane can correspond to an N-(diaminoalkyl)aminoalkyl alkoxysilane. In some aspects, the alkoxy groups can contain 1 to 6 carbons, or 2 to 6 carbons, or 1 to 4 carbons, or 2 to 4 carbons. In some aspects, each of the alkoxy groups attached to the silicon atom can have the same number of carbon atoms (e.g., all alkoxy groups are methoxy, or all alkoxy groups are ethoxy). It is noted that the alkyl groups can optionally be branched, unbranched, or a mixture of branched and unbranched.
The gelator or gelling agent corresponds to an acyclic polyalkoxysilane compound. The gelator can optionally correspond to an alkyl polyalkoxysilane, or the gelator can optionally correspond to an alkylamine alkoxysilane, or a combination thereof. An example of an alkyl polyalkoxysilane is 1,2-bis(triethoxysilyl)ethane. An example of an alkylamine polyalkoxysilane is N,N′bis[3-(triethoxysilyl)propyl]ethane-1,2-diamine. These example compounds are shown as the “gelator” compounds in
To form an organosilica compound, the alkoxy-substituted cyclic organosilane and the aminosilane precursor can be combined in a molar ratio of 1:0.5-3.0, or 1:1.0-3.0, or 1:0.5-2.0. The alkoxy-substituted cyclic organosilane and the gelator or gelling agent can be combined in a molar ratio of 1:0.2-0.8, or 1:0.2-0.6, or 1:0.4-0.8. To form the organosilica compound, the reagents can be mixed together in an aqueous solution at a pH of 10.5-12.5. The mixture can be mixed for 5.0 hours to 20 hours, such as overnight.
After this initial mixing, the mixture is aged to allow for gel formation. Ageing can be performed under a variety of conditions. For example, can be heated to a temperature of 50° C. to 150° C., or 70° C. to 150° C., or 50° C. to 110° C., or 70° C. to 110° C., and maintained at the temperature for 20 hours to 150 hours, or 20 to 60 hours. This produces a gel intermediate. Optionally, the heating of the mixture can be performed in a rotating oven to facilitate even heating.
After forming a gel intermediate, the gel intermediate can be dried using supercritical CO2, freeze drying, or a combination thereof. Preferably, drying can be performed using supercritical CO2. Both freeze drying and drying with supercritical CO2 can provide benefits for improving CO2 sorption (and/or sorption of other compounds). However, this benefit is larger when drying is performed using supercritical CO2.
Conventionally, the straightforward route for drying an intermediate gel is to heat the intermediate gel to convert the solvent (such as water) in the intermediate gel into a gas, which can then be purged from the gel. Unfortunately, performing the liquid-gas phase transition within the gel appears to alter the gel structure.
Another option for drying an intermediate gel after gel formation is to expose the gel to reduced pressure, such as a pressure of 10 kPa-a or less, in order to convert the liquid solvent in the intermediate gel into a vapor that can then be readily purged from the gel structure using a purge gas. However, this method still involves performing the liquid-gas phase transition within the gel structure.
For drying using supercritical CO2, the drying process is started by first removing water from the intermediate gel using an alcohol, such as methanol or ethanol. After displacing water with alcohol, the gel is rinsed with high pressure liquid CO2 to remove the alcohol. This leaves behind high pressure liquid CO2 in the gel structure. The high pressure liquid CO2 is then removed by increasing the temperature of the CO2 until the temperature is above the critical point temperature of CO2. The pressure is then reduced, followed by purging with a suitable gas (such as nitrogen). This results in the organosilica gel product. By increasing the temperature to above the critical point and then reducing the temperature, no phase transition occurs when changing from the initial high pressure liquid CO2 to higher temperature, lower pressure CO2. Avoiding this phase transition allows the CO2 to be converted into a gas while reducing or minimizing changes to the structure of the gel. It is noted that the critical point for CO2 is roughly 31° C. and 7.39 MPa.
During a supercritical CO2 drying process, the initial displacement of water via solvent exchange with alcohol can be performed using any convenient small alcohol or mixture of small alcohols. Examples of suitable alcohols include, but are not limited to, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, C4 alcohol, and combinations thereof. More generally, the alcohol can correspond to an alcohol (or mixture of alcohols) where the alcohol does not freeze at −57° C., which is the minimum temperature for formation of liquid CO2. The initial alcohol solvent exchange can be performed at a temperature of 0° C. to 30° C., or 5° C. to 30° C. It is noted that the solvent exchange should be performed at a high enough temperature that the water within the intermediate gel does not freeze. Any convenient pressure can be used for the alcohol solvent exchange. In some aspects, the alcohol solvent exchange can be performed at roughly ambient pressure, so a pressure of roughly 90 kPa-a or more, or 100 kPa-a or more. In other aspects, it can be convenient to perform the alcohol solvent exchange at a pressure that is similar to the pressure that will be used for the initial introduction of liquid CO2 into the gel. In such aspects, the pressure during the alcohol solvent exchange can be 0.8 MPa-a or higher, or 2.0 MPa-a or higher, or 4.0 MPa-a or higher or 7.4 MPa-a or higher, such as up to 10 MPa-a or possibly still higher. The solvent exchange can be performed for a sufficient amount of time to remove substantially all of the water from the gel structure. In some aspects, the solvent exchange with alcohol can be performed for 0.5 hours to 24 hours, or 1.0 hours to 24 hours, or 0.5 hours to 12 hours, or 1.0 hours to 12 hours. In some aspects, this can correspond to performing a plurality of washes with alcohol, such as up to 5, or up to 10.
After solvent exchange with alcohol, a second wash can be performed with fluid CO2, such as liquid CO2 and/or supercritical CO2. Because the small alcohols used in the alcohol solvent exchange have lower freezing points than water, the gel can be washed with the fluid CO2 at a temperature between −59° C. and 5.0° C. During the wash with fluid CO2, the pressure can be any convenient pressure where the CO2 is in a liquid state (or optionally a supercritical state) based on the temperature. In various aspects, the pressure during the liquid CO2 wash step can be 0.8 MPa-a or higher, or 2.0 MPa-a or higher, or 4.0 MPa-a or higher or 7.4 MPa-a or higher, such as up to 10 MPa-a or possibly still higher. The wash can be performed for a sufficient amount of time to remove substantially all of the alcohol wash from the gel structure. In some aspects, the wash with fluid CO2 can be performed for 1.0 hours to 12 hours, or 1.0 hours to 8.0 hours, or 1.0 hours to 4.0 hours, or 2.0 hours to 12 hours, or 2.0 hours to 8.0 hours, or 2.0 hours to 4.0 hours. Optionally, the wash with fluid CO2 can be performed iteratively, with between 1-3 washes with CO2 being performed before proceeding to the next step.
After washing with CO2, the pressure in the wash environment can be increased so that the pressure is above the critical point for CO2. The corresponds to increasing the pressure to 7.4 MPa-a or more. Higher values of pressure can be used, so long as the pressure does not cause substantial collapse of the gel structure. Thus, pressures of up to 20 MPa-a can be used, although achieving such pressures that are substantially above the critical point incurs additional energy cost with little or no additional benefit. It is noted that the increase in pressure can be performed in any convenient manner, so long as the CO2 does not undergo a phase transition to a solid or a gas during the increase. It is further noted that if the pressure during the CO2 was 7.4 MPa-a or higher, then no further pressure increase is needed.
The temperature in the wash environment can also be increased so that the temperature is above the critical point for CO2. The corresponds to increasing the temperature to 31° C. or more. Higher values of temperature can be used (such as up to 70° C.) although achieving such temperatures that are substantially above the critical point incurs additional energy cost with little or no additional benefit. In some aspects, the increase in pressure and temperature can be performed sequentially, so that the pressure is increased first, and then the temperature is increased. In other aspects, the temperature and pressure increase(s) can be performed in any convenient manner, so long as no phase transition for CO2 occurs during the increase(s) in temperature and pressure. It is noted that the path to achieving the pressure and temperature combination that is greater than the critical point for CO2 may include steps where the pressure or temperature are decreased.
After increasing the temperature and/or pressure in the wash environment to a combination of temperature and pressure beyond the CO2 critical point, the pressure can be decreased while the temperature remains above the critical point so that the CO2 is in the “gas phase” portion of the phase diagram after decreasing the pressure. Once the pressure in the wash environment is in the “gas phase” portion of the phase diagram, any convenient combination of temperature and/or pressure changes can be used to reduce the density of the CO2 to a point where the CO2 can be removed. In some aspects, the CO2 can be purged with a purge stream (such as N2 or air). Additionally or alternately, the pressure can be reduced to a pressure below 100 kPa-a, or below 90 kPa-a, such as down to 1.0 kPa-a or possibly still lower, to remove the CO2 in a vacuum environment. Of course, a combination of a purge gas and a reduced pressure environment can also be used. Still another option is to vent the CO2, without the need for either a purge or reducing the pressure below 100 kPa-a.
Freeze drying provides an alternative method of trying to avoid a liquid-gas phase transition while removing liquids from the gel structure. Instead of going around the supercritical point, a freeze drying process converts the liquid in the gel to a solid, and then removes the solid via a solid-gas phase transition. The are several options for performing the freeze drying. One option is to directly freeze the water in the gel, and then reduce the pressure in the wash environment to a sufficiently low pressure that the ice sublimates (i.e., passes directly from solid to gas phase). Alternatively, the water can be removed by rinsing with one or more secondary wash mediums, such as small alcohols or CO2. The temperature and pressure can then be modified so that the secondary wash medium remaining in the gel is converted to a solid, followed by a second modification of the pressure to sublimate the solid to a gas. It is noted that some disruption of the resulting gel structure can still occur during the solid-gas phase transition in the freeze-drying method. After sublimating the wash medium, the gas can be removed from the gel by reducing the pressure to 70 kPa-a or less, or 50 kPa-a or less, such as down to 1.0 kPa-a or possibly still lower. Optionally, a purge gas (such as N2 or air) can be used to assist with removing the gas from the gel structure.
The organosilica materials made by the methods described herein can be characterized as described in the following sections.
The organosilica materials described herein can exhibit powder X-ray diffraction patterns with one broad peak between about 1 and about 4 degrees 2θ, particularly one peak between about 1 and about 3 degrees 2θ. Additionally or alternatively, in the 0.5 to 12 degrees 2θ range, the organosilica materials can exhibit substantially no peaks, or in the range of about 3 to about 12 degrees 2θ, about 4 to about 12 degrees 2θ, in the range of about 5 to about 12 degrees 2θ, in the range of about 6 to about 12 degrees 2θ, in the range of about 7 to about 12 degrees 2θ, in the range of about 8 to about 12 degrees 2θ, in the range of about 9 to about 12 degrees 2θ, in the range of about 10 to about 12 degrees 2θ, or in the range of about 11 to about 12 degrees 2θ.
The organosilica materials can be in a mesoporous form. As indicated previously, the term mesoporous refers to solid materials having pores with a diameter within the range of from about 2 nm to about 50 nm. The average pore diameter of the organosilica material can be determined, for example, using nitrogen adsorption-desorption isotherm techniques within the expertise of one of skill in the art. In this discussion, the average pore diameter of the organosilica material can be determined based on a procedure similar to the procedure in UOP 425, but with an activation procedure that corresponded to exposing the material to a temperature of 140° C. for 4 hours under vacuum prior to obtaining an isotherm. It is noted that this modified version of UOP 425 is used herein even for pore sizes below 1.0 nm.
The organosilica material can have an average pore diameter of 2.0 nm to 50 nm, or 2.0 nm to 20 nm, or 2.0 nm to 10 nm, or 5.0 nm to 50 nm, or 5.0 nm to 20 nm, or 10 nm to 50 nm. In some alternative aspects, the organosilica material can have sufficient micropore volume that the average pore diameter may be less than 2.0 nm. Thus, in some alternative aspects, the organosilica material can have an average pore diameter of 1.2 nm to 20 nm, or 1.2 nm to 10 nm, or 1.2 nm to 5.0 nm, or 1.5 nm to 20 nm, or 1.5 nm to 10 nm, or 1.5 nm to 5.0 nm, or 2.0 nm to 5.0 nm.
The surface area of the organosilica material can be determined, for example, using nitrogen adsorption-desorption isotherm techniques within the expertise of one of skill in the art, such as the BET (Brunauer Emmet Teller) method. This method may determine a total surface area, an external surface area, and a microporous surface area. As used herein, and unless otherwise specified, “total surface area” refers to the total surface area as determined by the BET method. As used herein, and unless otherwise specified, “microporous surface area” refers to microporous surface are as determined by the BET method. As used herein, and unless otherwise specified, “microporous surface area” refers to microporous surface are as determined by the BET method in ASTM UOP 425, with the modification to the activation procedure (4 hours at 140° C. under vacuum) described above.
In various aspects, the organosilica material can have a total surface area of 200 m2/g to about 2,000 m2/g, or 200 m2/g to about 1,500 m2/g, or 200 m2/g to 1000 m2/g, or 400 m2/g to about 2,000 m2/g, or 400 m2/g to about 1,500 m2/g, or 400 m2/g to 1000 m2/g, or 600 m2/g to 2,000 m2/g, or 600 m2/g to 1,500 m2/g, or 800 m2/g to 2000 m2/g, or 800 m2/g to 1,500 m2/g.
The pore volume of the organosilica material can be determined according to the method in ASTM UOP 425, with the modification to the activation procedure (4 hours at 140° C. under vacuum) described above. In various aspect, the organosilica material can have a pore volume of 0.75 cm3/g to 3.0 cm3/g, or 1.0 cm3/g to 3.0 cm3/g, or 1.5 cm3/g to 3.0 cm3/g, or 2.0 cm3/g to 3.0 cm3/g, or 0.75 cm3/g to 2.7 cm3/g, or 1.0 cm3/g to 2.7 cm3/g, or 1.5 cm3/g to 2.7 cm3/g, or 2.0 cm3/g to 2.7 cm3/g.
In some aspects, an organosilica material can be used in a gas separation process. The gas separation process can comprise contacting a gas mixture containing at least one contaminant with the organosilica material.
As an example, one type of separation can be a method for abating CO2 from a flue gas in which the flue gas is contacted with an amine-functionalized organosilica material as described herein to reversibly adsorb CO2 from the flue gas, capturing >90% by volume, preferably >99% by volume, CO2 emissions such that the emissions are negative, resulting in direct CO2 capture from the air, thereby generating an adsorption material enriched for CO2 and then stripping a major portion of the CO2 from the adsorption material enriched for CO2 using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof. A typical CO2 content for air is roughly 400 vppm, or this type of separation corresponds to separating CO2 from a gas flow having a CO2 content of 200 vppm to 600 vppm.
Another type of separation can be a method for capturing CO2 from air, also known as direct air capture, in which air is contacted with an amine-functionalized organosilica material as described herein to reversibly adsorb CO2 from air, capturing >50% by volume, preferable >75% by volume, CO2 emissions, or stated differently, reducing CO2 concentrations in air to less than about 200 ppmv, preferably to less than 100 ppmv, such that the emissions are negative, resulting in direct CO2 capture from the air, thereby generating an adsorption material enriched for CO2. It would be understood by a person of skill in the art that as the base concentration changes, the capture rate also changes. A major portion of the CO2 can then stripped from the adsorption material enriched for CO2 using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof.
Still another type of application is carbon capture from powerplant exhaust, such as coal flue gas. The increasing atmospheric levels of carbon dioxide (CO2), which are likely contributing to global climate change, warrant new strategies for reducing CO2 emissions from point sources such as power plants. In particular, coal-fueled power plants are responsible for a substantial portion of global anthropogenic energy supply CO2 emissions. Thus, there remains a continuing need for the development of new adsorbents for carbon capture from coal flue gas. An example of a gas stream corresponding to a coal flue gas can include CO2 (˜15-16%), O2 (˜3-4%), H2O (˜5-7%), N2 (˜70-75%), and trace impurities (e.g. SO2, NOx) at ambient pressure and 40° C. For a temperature swing adsorption process for separating CO2 from a flue gas (such as coal flue gas), it can be beneficial to have an adsorbent that possesses one or more the following properties: (a) a high working capacity with a minimal temperature swing, in order to minimize regeneration energy costs; (b) high selectivity for CO2 over the other constituents of coal flue gas; (c) 90% (or greater) capture of CO2 under flue gas conditions; (d) effective performance under humid conditions; and (d) long-term stability to adsorption/desorption cycling under humid conditions.
More generally, another example of a separation can be a method for abating CO2 from a flue gas, such as natural gas flue gas. Generally, a combustion flue gas can correspond to a gas containing 4.0 vol % or more of CO2, with higher CO2 concentrations possible for flue gases formed by burning hydrocarbons other than methane or natural gas, such as coal or heavy oils. In such embodiments, the flue gas is contacted with an amine-functionalized organosilica material as described herein to reversibly adsorb CO2 from the flue gas thereby generating an adsorption material enriched for CO2 and then stripping a major portion of the CO2 from the adsorption material enriched for CO2 using a using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof.
In some aspects, a separation can be used to sequester carbon dioxide produced by a source. In such aspects, a method can include exposing the carbon dioxide to an amine-functionalized organosilica material as described herein whereby the carbon dioxide is reversibly sequestered into the adsorption material. In some such embodiments, the method further comprises regenerating the adsorption material enriched for CO2 using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof.
More generally, in some aspects, an amine-functionalized organosilica material as described herein can be used in a method of sequestering carbon dioxide from a multi-component gas mixture. In such aspects, a multi-component gas mixture can include CO2 and at least one of N2, H2O, and O2. The multi-component gas mixture is exposed to an amine-functionalized organosilica material as described herein whereby a least fifty percent, at least sixty percent, or at least eighty percent of the carbon dioxide within the multi-component gas mixture is reversibly sequestered into the adsorption material. In some such embodiments, the method further comprises regenerating the adsorption material enriched for CO2 using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof.
F. Gas Separation Processes—Separation of CO2 from Methane-Containing Gases
Another option for performing a gas separation process is to use a swing adsorption processes, such as pressure swing adsorption (PSA) and temperature swing adsorption (TSA). All swing adsorption processes typically have an adsorption step in which a feed mixture (typically in the gas phase) is flowed over an adsorbent to preferentially adsorb a more readily adsorbed component relative to a less readily adsorbed component. A component may be more readily adsorbed because of kinetic or equilibrium properties of the adsorbent. The adsorbent (e.g., the organosilica material described herein) can typically be contained in a contactor that is part of the swing adsorption unit. The contactor can typically contain an engineered structured adsorbent bed or a particulate adsorbent bed. The bed can contain the adsorbent (e.g., the organosilica material described herein) and other materials such as other adsorbents, mesopore filling materials, and/or inert materials used to mitigated temperature excursions from the heat of adsorption and desorption. Other components in the swing adsorption unit can include, but are not necessarily limited to, valves, piping, tanks, and other contactors. Examples of swing adsorption processes are described in detail in, for example, U.S. Pat. Nos. 8,784,533; 8,784,534; 8,858,683; and 8,784,535. Examples of processes that can be used herein either separately or in combination are PSA, TSA, pressure temperature swing adsorption (PTSA), partial purge displacement swing adsorption (PPSA), PPTSA, rapid cycle PSA (RCPSA), RCTSA, RCPPSA and RCPTSA.
PSA processes rely on the fact that gases under pressure tend to be adsorbed within the pore structure of the adsorbent materials (e.g., the organosilica material described herein). Typically, the higher the pressure, the greater the amount of targeted gas component that will be adsorbed. When the pressure is reduced, the adsorbed targeted component is typically released, or desorbed. PSA processes can be used to separate gases of a gas mixture, because different gases tend to fill the pores or free volume of the adsorbent to different extents due to either the equilibrium or kinetic properties of the adsorbent. In many important applications, to be described as “equilibrium-controlled” processes, the adsorptive selectivity is primarily based upon differential equilibrium uptake of the first and second components. In another important class of applications, to be described as “kinetic-controlled” processes, the adsorptive selectivity is primarily based upon the differential rates of uptake of the first and second components.
If a gas mixture, such as natural gas, is passed under pressure through a vessel containing a polymeric or microporous adsorbent that is more selective towards carbon dioxide than it is for methane, at least a portion of the carbon dioxide can be selectively adsorbed by the adsorbent, and the gas exiting the vessel can be enriched in methane. When the adsorbent (e.g., the organosilica material described herein) reaches the end of its capacity to adsorb carbon dioxide, it can be regenerated by reducing the pressure, thereby releasing the adsorbed carbon dioxide. The adsorbent can then typically purged and repressurized and ready for another adsorption cycle.
TSA processes also rely on the fact that gases under pressure tend to be adsorbed within the pore structure of the adsorbent materials. When the temperature of the adsorbent (e.g., the organosilica material described herein) is increased, the adsorbed gas is typically released, or desorbed. By cyclically swinging the temperature of adsorbent beds, TSA processes can be used to separate gases in a mixture when used with an adsorbent selective for one or more of the components in a gas mixture. Partial pressure purge displacement (PPSA) swing adsorption processes regenerate the adsorbent with a purge. Rapid cycle (RC) swing adsorption processes complete the adsorption step of a swing adsorption process in a short amount of time. For kinetically selective adsorbents, it can be preferable to use a rapid cycle swing adsorption process. If the cycle time becomes too long, the kinetic selectivity can be lost. These swing adsorption protocols can be performed separately or in combinations. Examples of processes that can be used herein either separately or in combination are PSA, TSA, pressure temperature swing adsorption (PTSA), partial purge displacement swing adsorption (PPSA), PPTSA, rapid cycle PSA (RCPSA), RCTSA, vacuum pressure swing adsorption (VPSA), RCPPSA and RCPTSA.
In PSA processes, a feed gas mixture containing the first and second gas components is separated by cyclic variations of pressure coordinated with cyclic reversals of flow direction in a flow path contacting a fixed bed of the adsorbent material in an adsorber vessel. In the case of TSA or PPSA processes, cyclic variations of temperature and/or partial pressure of the gas components may be coordinated with gas flow through a flow path to perform a separation. The process in any specific PSA application operates at a cyclic frequency characterized by its period, and over a pressure envelope between a first relatively higher pressure and a second relatively lower pressure. Separation in PSA is achieved by coordinating the pressure variations with the flow pattern within the flow path, so that the gas mixture in the flow path is enriched in the second component (owing to preferential adsorptive uptake of the first component in the adsorbent material) when flowing in a first direction in the flow path, while the gas mixture is enriched in the first component (which has been desorbed by the adsorbent material) when flowing in the opposite direction in the flow path. In order to achieve separation performance objectives (i.e. product gas purity, recovery and productivity), process parameters and operating conditions should be designed to achieve a sufficiently high adsorptive selectivity of the first and second components over the adsorbent material, at the cyclic frequency and within the pressure envelope.
Swing adsorption processes can be applied to remove a variety of target gases, also referred to as “contaminant gas” from a wide variety of gas mixtures. Typically, in binary separation systems, the “light component” as utilized herein is taken to be the species or molecular component(s) not preferentially taken up by the adsorbent in the adsorption step of the process. Conversely in such binary systems, the “heavy component” as utilized herein is typically taken to be the species or molecular component(s) preferentially taken up by the adsorbent in the adsorption step of the process. However, in binary separation systems where the component(s) that is(are) preferentially adsorbed has(have) a lower molecular weight than the component(s) that is(are) not preferentially adsorbed, those descriptions may not necessarily correlate as disclosed above.
An example of gas mixture that can be separated in the methods described herein is a gas mixture comprising CH4, such as a natural gas stream. A gas mixture comprising CH4 can contain significant levels of contaminants such as H2O, H2S, CO2, N2, mercaptans, and/or heavy hydrocarbons. Additionally or alternatively, the gas mixture can comprise NOx and/or SOx species as contaminants, such as a waste gas stream, a flue gas stream and a wet gas stream. As used herein, the terms “NOx,” and “NOx” species refers to the various oxides of nitrogen that may be present in waste gas, such as waste gas from combustion processes. The terms refer to all of the various oxides of nitrogen including, but not limited to, nitric oxide (NO), nitrogen dioxide (NO2), nitrogen peroxide (N2O), nitrogen pentoxide (N2O5), and mixtures thereof. As used herein, the terms “SOx,” and “SOx species,” refers to the various oxides of sulfur that may be present in waste gas, such as waste gas from combustion processes. The terms refer to all of the various oxides of sulfur including, but not limited to, SO, SO2, SO3, SO4, S7O2 and S6O2. Thus, examples of contaminants include, but are not limited to H2O, H2S, CO2, N2, mercaptans, heavy hydrocarbons, NOx and/or SOx species. In particular, the gas mixture may comprise CH4 and the at least one contaminant is CO2 and/or H2S.
An example of a method for separating CO2 from a methane-containing stream is removing CO2 from a biogas. The method comprises contacting the biogas with an amine-functionalized organosilica material as described herein to reversibly adsorb CO2 from the biogas thereby generating an adsorption material enriched for CO2 and a residual gas that is greater than 98 percent pure methane. In some such embodiments, the method further comprises stripping a major portion of the CO2 from the adsorption material enriched for CO2 using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof.
Another example of a method for separating CO2 from a methane-containing stream is removing CO2 from a hydrocarbon reservoir. The method comprises contacting the hydrocarbon reservoir with an amine-functionalized organosilica material as described herein to reversibly adsorb CO2 from the hydrocarbon reservoir thereby generating an adsorption material enriched for CO2. In some such embodiments, the method further comprises stripping a major portion of the CO2 from the adsorption material enriched for CO2 using a temperature swing adsorption method, vacuum swing adsorption method, a pressure swing adsorption method, a concentration swing adsorption method, or a combination thereof.
In various aspects, a process for selectively separating a contaminant from a feed gas mixture is provided herein. The process may comprise: a) contacting the feed gas mixture under sorption conditions with organosilica material described herein; b) adsorbing the contaminant into/onto the organosilica material described herein; c) subjecting the organosilica material described herein to desorption conditions by which at least a portion of the sorbed contaminant is desorbed; and d) retrieving a contaminant-rich product stream that has a higher mol % of contaminant than the feed gas mixture. The feed gas mixture may be any of the gas mixtures described above. Particularly, the feed gas mixture may comprise CH4. The contaminant may be any of the contaminants described above, e.g., CO2, H2S, etc.
It may be desirable to operate with a multiplicity of structure adsorbent beds, with several coupled in a heating/cooling operation and others involved in adsorption (and/or desorption). In such an operation, the adsorbent bed can be substantially cooled by a circulating heat transfer medium before it is switched into service for adsorption. One advantage of such an operation can be that the thermal energy used to swing the bed is retained in the heat transfer medium. If adsorption were to proceed simultaneously with cooling, then a substantial part of the heat in the bed could be lost to the adsorbate-free feed, and a higher heat load could be needed to restore the high temperature of the heat transfer medium.
Adsorptive kinetic separation (AKS) processes, as described above, are useful for development and production of hydrocarbons, such as gas and oil processing. For example, as described in U.S. Patent Application Publication No. 2013/032716, the AKS processes described herein can use one or more kinetic swing adsorption process, such as pressure swing adsorption (PSA), thermal swing adsorption (TSA), calcination, and partial pressure swing or displacement purge adsorption (PPSA), including combinations of these processes; each swing adsorption process may be utilized with rapid cycles, such as using one or more rapid cycle pressure swing adsorption (RC-PSA) units, with one or more rapid cycle temperature swing adsorption (RC-TSA) units or with one or more rapid cycle partial pressure swing adsorption (RC-PPSA) units; exemplary kinetic swing adsorption processes are described in U.S. Pat. Nos. 7,959,720; 8,545,602; 8,529,663; 8,444,750; and 8,529,662. The provided processes can be useful for rapid, large scale, efficient separation of a variety of target gases from gas mixtures.
The provided processes and apparatuses may be used to prepare natural gas products by removing contaminants. The provided processes and apparatuses can be useful for preparing gaseous feed streams for use in utilities, including separation applications such as dew point control, sweetening/detoxification, corrosion protection/control, dehydration, heating value, conditioning, and purification. Examples of utilities that utilize one or more separation applications can include generation of fuel gas, seal gas, non-potable water, blanket gas, instrument and control gas, refrigerant, inert gas, and hydrocarbon recovery. Exemplary “not to exceed” product (or “target”) acid gas removal specifications can include: (a) 2 vol % CO2, 4 ppm H2S; (b) 50 ppm CO2, 4 ppm H2S; or (c) 1.5 vol % CO2, 2 ppm H2S.
The provided processes and apparatuses may also be used to remove acid gas from hydrocarbon streams. Acid gas removal technology becomes increasingly important as remaining gas reserves exhibit higher concentrations of acid (sour) gas resources. Hydrocarbon feed streams can vary widely in amount of acid gas, such as from several parts per million to 90 vol %. Non-limiting examples of acid gas concentrations from exemplary gas reserves can include concentrations of at least: (a) 1 vol % H2S, 5 vol % CO2; (b) 1 vol % H2S, 15 vol % CO2; (c) 1 vol % H2S, 60 vol % CO2; (d) 15 vol % H2S, 15 vol % CO2; or (e) 15 vol % H2S, 30 vol % CO2.
One or more of the following may be utilized with the processes and apparatuses provided herein, to prepare a desirable product stream, while maintaining relatively high hydrocarbon recovery: (a) removing acid gas with RC-TSA (rapid cycle—temperature swing adsorption); (b) using a mesopore filler to reduce the amount of trapped methane in the adsorbent bed and increase the overall hydrocarbon recovery; depressurizing one or more RC-TSA units in multiple steps to intermediate pressures so that the acid gas exhaust can be captured at a higher average pressure, thereby decreasing the compression required for acid gas injection; pressure levels for the intermediate depressurization steps may be matched to the interstage pressures of the acid gas compressor to optimize the overall compression system; (d) using exhaust or recycle streams to minimize processing and hydrocarbon losses, such as using exhaust streams from one or more RC-TSA units as fuel gas instead of re-injecting or venting; (e) using multiple adsorbent particles in a single bed to remove trace amounts of first contaminants, such as H2S, before removal of a second contaminant, such as CO2; such segmented beds may provide rigorous acid gas removal down to ppm levels with RC-TSA units with minimal purge flow rates; (f) using feed compression before one or more RC-TSA units to achieve a desired product purity; (g) contemporaneous removal of non-acid gas contaminants such as mercaptans, COS, and BTEX; selection processes and materials to accomplish the same; (h) selecting a cycle time and cycle steps based on adsorbent material kinetics; and (i) using a process and apparatus that uses, among other equipment, two RC-TSA units in series, wherein the first RC-TSA unit cleans a feed stream down to a desired product purity and the second RC-TSA unit cleans the exhaust from the first unit to capture methane and maintain high hydrocarbon recovery; use of this series design may reduce the need for a mesopore filler.
The processes, apparatuses, and systems provided herein can be useful in large gas treating facilities, such as facilities that process more than five million standard cubic feet per day (MSCFD) of natural gas, for example more than 15 MSCFD, more than 25 MSCFD, more than 50 MSCFD, more than 100 MSCFD, more than 500 MSCFD, more than one billion standard cubic feet per day (BSCFD), or more than two BSCFD.
CO2 adsorption work was done with a Quantchrom autosorb iQ2. All the samples were pre-treated at 120° C. in vacuum for 3 hours before collecting the CO2 isotherm at different temperatures.
The nitrogen adsorption/desorption analyses was performed with different instruments, e.g. TriStar 3000, TriStar 113020 and Autosorb-1. All the samples were pre-treated at 120° C. in vacuum for 4 hours before collecting the N2 isotherm. The analysis program calculated the experimental data and report BET surface area (total surface area), microporous surface area (S), total pore volume, pore volume for micropores, average pore diameter (or radius), etc.
The organosilica materials in these examples were made using the method illustrated in
At this point, one of several drying methods was used to form the final organosilica material. Gel samples were dried using supercritical CO2 drying, freeze-drying, or by heating to 120° C. at a pressure below 80 kPa-a (representative of conventional drying conditions for many types of organosilica gels).
The organosilica materials produced using the various drying methods were then characterized.
As shown in
Without being bound by any particular theory, it is believed that by avoiding liquid-gas phase transitions during the drying process, the amount of damage to a gel structure can be reduced, thereby preserving an increased amount of surface area and/or pore volume.
It has been discovered that the structural differences caused by different drying methods result in different sorption behavior for the resulting organosilica materials.
As shown in
Based in part on the increased surface area and pore volume, the organosilica materials formed using supercritical CO2 drying also provide an increase in CO2 utilization during sorption. Based on the nature of the binding interaction, a CO2/N ratio of 0.5 corresponds to full loading of the binding sites with CO2.
To further illustrate the differences in various drying techniques,
The benefits of using supercritical CO2 for drying were maintained when using different types of amine-functionalizing agents. In the examples presented so far, N-(aminoethyl)aminopropyl trialkoxysilane (“TDA”) was used as the aminosilane precursor functionalizing agent. Similar results were obtained when using two other types of aminosilane functionalizing agents, corresponding to N-(aminohexyl)aminopropyl trialkoxysilane (“C3C6DA”) and N-(aminohexyl)aminomethyl trialkoxysilane (“C1C6DA”)
To make the organosilica materials for
Embodiment 1. An organosilica material comprising a polymer of at least one monomer of Formula (I),
wherein Z1, Z2, Z3, Z4, Z5, and Z6 each independently represent a hydrogen atom, a C1-C4 alkyl group, a bond to a silicon atom of another monomer of Formula (I), a bond to an aminosilyl group, a bond to a silicon atom that is bonded to three alkoxy groups, or a bond to a silicon atom of a secondary monomer comprising an acyclic alkoxy silane, wherein R11, R12, R13, R14, R15, and R16 each independently represent a hydrogen atom or a C1-C4 alkyl group, and wherein the organosilica material comprises a nitrogen content of 4.0 wt % to 9.5 wt %, a surface area of 300 m2/g or more, a pore volume of 0.75 cm3/g or more.
Embodiment 2. The organosilica material of Embodiment 1, wherein the nitrogen content is 6.5 wt % to 9.5 wt %, or wherein the nitrogen content is 4.4 wt % to 8.0 wt %.
Embodiment 3. The organosilica material of any of the above embodiments, wherein the organosilica material comprises a surface area of 400 m2/g or more, or wherein the organosilica material comprises a pore volume of 1.0 cm3/g or more, or a combination thereof.
Embodiment 4. The organosilica material of any of the above embodiments, wherein R11, R12, R13, R14, R15, and R16 each represent a hydrogen atom.
Embodiment 5. The organosilica material of any of the above embodiments, wherein the aminosilane comprises a N-(aminoalkyl)aminoalkyl polyalkoxysilane.
Embodiment 6. The organosilica material of any of the above embodiments, wherein the aminosilane comprises a trialkoxysilane.
Embodiment 7. The organosilica material of any of the above embodiments, wherein Z1, Z2, Z3, Z4, Z5, and Z6 each independently represent a hydrogen atom, a C1-C4 alkyl group, a bond to a silicon atom of another monomer of Formula (I), or a bond to an aminosilyl group.
Embodiment 8. The organosilica material of any of the above embodiments, wherein a molar ratio of the at least one monomer of Formula 1 to the secondary monomer is 2.0 or more, or wherein only one of Z1, Z2, Z3, Z4, Z5, and Z6 represents a silicon atom bonded to three alkoxy groups, or a combination thereof.
Embodiment 9. The organosilica material of Embodiment 8, wherein the secondary monomer comprises an acyclic alkoxy aminosilane.
Embodiment 10. The organosilica material of any of the above embodiments, wherein the organosilica material is formed by drying an intermediate gel using supercritical CO2, and wherein optionally the intermediate gel is formed by condensation of the polymer from a mixture comprising an alkoxy-substituted trisilacyclohexane and a precursor of the aminosilane, the mixture optionally further comprising a gelator comprising a precursor of the secondary monomer.
Embodiment 11. The organosilica material of any of the above embodiments, wherein the organosilica material comprises a CO2 capacity of greater than 1.0 mmol CO2/g organosilica material in an environment comprising 4.0 vol % CO2 at 30° C., and wherein optionally the organosilica material, at maximum CO2 capacity, has an amine utilization of greater than 0.4, the amine utilization defined as the molar ratio of CO2 sorbed by the organosilica material to the nitrogen in the organosilica material.
Embodiment 12. A gas separation process comprising contacting a gas mixture containing at least one contaminant with the organosilica material of any of the above embodiments.
Embodiment 13. The process of Embodiment 12, wherein the gas mixture comprises CH4 and the at least one contaminant is CO2 and/or H2S.
Embodiment 14. The process of Embodiment 12, wherein the gas mixture comprises a flue gas containing 4.0 vol % or more of CO2, or wherein the gas mixture comprises air having a CO2 content of 600 vppm or less.
Embodiment 15. The process of any of Embodiments 12-14, wherein the process comprises PSA, TSA, PPSA, PTSA, RCPSA, RCTSA, RC-PPSA or RC-PTSA.
All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
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 app. No. 63/590,593, filed Oct. 16, 2023, and titled “AMINE-FUNCTIONAL AEROGELS FOR ACID GAS REMOVAL,” the entire contents of which is incorporated herein by reference
| Number | Date | Country | |
|---|---|---|---|
| 63590593 | Oct 2023 | US |
