COMPOSITE PARTICLES AND THEIR USE IN THE SELECTIVE CAPTURE AND RELEASE OF CARBON DIOXIDE WITH USE OF DIELECTRIC HEATING

Abstract

A carbon capture composite particle comprising a core and a shell, wherein: (i) the core of the carbon capture composite particle comprises a liquid sorbent reactive with carbon dioxide; and (ii) the shell of the carbon capture composite particle encapsulates said core and comprises a multiplicity of hydrophobic-coated oxide particles, wherein gas-permeable spacings are present between the hydrophobic-coated oxide particles, and said hydrophobic-coated oxide particles have a main group or transition metal oxide inner portion encapsulated by a coating of hydrophobic molecules. Also described herein is a method for capturing carbon dioxide by contacting a gaseous source containing CO.sub.2 with the above-described carbon capture particles. Also described herein is an apparatus with a microwave-transparent or radiofrequency-transparent column (or window in the column) for regenerating carbon capture particles that have been reacted with CO.sub.2 by exposing the particles to microwave or radiofrequency electromagnetic radiation for direct conductive heating.

Claims

1. A carbon capture composite particle composition comprising a core and a shell, wherein: (i) the core of said carbon capture composite particle comprises a liquid sorbent reactive with carbon dioxide; and (ii) the shell of said carbon capture composite particle encapsulates said core and comprises a multiplicity of hydrophobic-coated oxide particles, wherein gas-permeable spacings are present between the hydrophobic-coated oxide particles, and said hydrophobic-coated oxide particles have a main group or transition metal oxide inner portion encapsulated by a coating of hydrophobic molecules.

2. The composition of claim 1, wherein the carbon capture composite particle further comprises magnetic nanoparticles embedded in the core or shell of the carbon capture particle.

3. The composition of claim 1, wherein said liquid sorbent is an ionic liquid.

4. The composition of claim 3, wherein the ionic liquid sorbent is an imidazolium ionic liquid.

5. The composition of claim 4, wherein the imidazolium ionic liquid is 1-ethyl-3-methylimidazolium 2-cyanopyrrolide.

6. The composition of claim 1, wherein said liquid sorbent is a deep eutectic solvent.

7. The composition of claim 6, wherein the deep eutectic solvent is selected from the group consisting of choline chloride-monoethanolamine, glyceline, reline, piperazine glyceline, tetraethylenepentamine chloride-thymol, choline chloride-ethanolamine-urea, methyltriphenylphosphonium bromide-ethylene glycol, methyltriphenylphosphonium bromide-glycerol, methyltriphenylphosphonium bromide-diethylene glycol, and tetrapropylammonium chloride-ethanolamine.

8. The composition of claim 1, wherein said liquid sorbent is an alkylamine solvent.

9. The composition of claim 1, wherein said hydrophobic-coated oxide particles are hydrophobic-coated silica particles.

10. The composition of claim 1, wherein said hydrophobic-coated oxide particles are alkyl-coated oxide particles.

11. The composition of claim 1, wherein said spacings have a size in a range of 0.1-1000 nm.

12. The composition of claim 1, wherein said hydrophobic-coated oxide particles have a size in a range of 1-1000 nm.

13. The composition of claim 1, wherein the carbon capture (core-shell) composite particle has a size in a range of 0.01-1000 microns.

14. The composition of claim 2, wherein the magnetic particles are paramagnetic or superparamagnetic.

15. The composition of claim 14, wherein the paramagnetic or superparamagnetic particles have an iron-containing composition.

16. The composition of claim 1, wherein the hydrophobic-coated oxide particles are present in an amount of 30-90 wt % of the carbon capture particle.

17. A method for capturing carbon dioxide, the method comprising contacting a gaseous source containing CO.sub.2 with a carbon capture composite particle composition comprising a core and a shell encapsulating the core to result in capture of CO.sub.2 from the gaseous source in the carbon capture composite particle, wherein: (i) the core of said carbon capture composite particle comprises a liquid sorbent reactive with CO.sub.2 and forms a sorbent-CO.sub.2 complex upon contact with CO.sub.2; and (ii) the shell of said carbon capture composite particle encapsulates said core and comprises a multiplicity of hydrophobic-coated oxide particles, wherein gas-permeable spacings are present between the hydrophobic-coated oxide particles to permit passage of the gaseous source to the liquid sorbent in the core, and said hydrophobic-coated oxide particles have a main group or transition metal oxide inner portion encapsulated by a coating of hydrophobic molecules.

18. The method of claim 17, wherein the carbon capture composite particle further comprises magnetic particles embedded in the core or shell of the carbon capture particle.

19. The method of claim 17, wherein said liquid sorbent is an ionic liquid.

20. The method of claim 17, wherein said liquid sorbent is a deep eutectic solvent.

21. The method of claim 17, wherein said liquid sorbent is an alkylamine solvent.

22. The method of claim 17, wherein said hydrophobic oxide particles are hydrophobic silica particles.

23. The method of claim 17, further comprising regenerating the liquid sorbent in the sorbent-CO.sub.2 complex by exposing said sorbent-CO.sub.2 complex to microwave or radiofrequency radiation.

24. The method of claim 23, wherein the regenerated liquid sorbent is re-used to capture CO.sub.2 and form a complex therewith.

25. An apparatus for regenerating a sorbent liquid in a sorbent-CO.sub.2 complex, the apparatus comprising: (i) a column for housing the sorbent-CO.sub.2 complex and through which a gas can flow, wherein said column is partially or completely microwave-transparent or radiofrequency-transparent to permit microwave or radiofrequency radiation to be transmitted through the column to contact the sorbent-CO.sub.2 complex; and (ii) a device for generating microwave or radiofrequency radiation.

26. The apparatus of claim 25, wherein the microwave-transparent or radiofrequency-transparent column has a polytetrafluoroethylene (PTFE) composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1. Schematic representation of a method for preparing carbon capture composite (CCC) particles having a core-shell arrangement.

[0019] FIG. 2. Schematic of a custom apparatus for breakthrough analysis with microwave (MW) regeneration. Sample column is expanded.

DETAILED DESCRIPTION

[0020] In a first aspect, the present disclosure is directed to a carbon capture composite (CCC) particle (or carbon capture particle) composition. The CCC particle has a core-shell composition in which the core portion of the CCC particle is encapsulated by the shell portion. The CCC particles generally have a size within a range of 0.01-1,000 microns. In more particular embodiments, the CCC particles have a size in a range of 0.01-500 microns, 0.01-250 microns, 0.01-100 microns, 0.01-50 microns, 0.01-10 microns, 0.1-500 microns, 0.1-250 microns, 0.1-100 microns, 0.1-50 microns, 0.1-10 microns, 1-1000 microns, 1-500 microns, 1-250 microns, 1-100 microns, 1-50 microns, 1-10 microns, 10-1000 microns, 10-500 microns, 10-250 microns, 10-100 microns, or 10-50 microns.

[0021] The core of the carbon capture particle contains a liquid sorbent reactive with carbon dioxide. By being reactive with carbon dioxide, the liquid sorbent binds with carbon dioxide to form a carbamate, bicarbonate, or carbonate salt. The liquid sorbent typically includes a primary amine, secondary amine, tertiary amine (or hindered amine), aryl amine, and/or an imide group to be reactive with carbon dioxide. The liquid sorbent may be, for example, an ionic liquid, a deep eutectic solvent, or alkylamine solvent.

[0022] In a first set of embodiments, the liquid sorbent in the core is or includes an ionic liquid that is reactive with carbon dioxide. As well known in the art, the term ionic liquid refers to an ionic compound (i.e., compound containing a cation associated with an anion) that is liquid at or around room temperature without being dissolved in a liquid solvent. In some embodiments, the ionic liquid contains an imidazolium, ammonium, piperidinium, piperazinium, pyridinium, pyrrolidinium, phosphonium, or sulfonium cationic portion. In separate or further embodiments, the ionic liquid includes a N-heterocyclic (e.g., cyanopyrrolide), amino acid, tetrafluoroborate, hexafluorophosphate, or sulfonylimide (e.g., Tf.sub.2N) type of anion. Ionic liquids containing any combination of cation and anion provided above are considered herein. Some examples of ionic liquids that can function as carbon capture sorbents include the class of 1,3-dialkylimidazolium 2-cyanopyrrolides (e.g., 1-ethyl-3-methylimidazolium 2-cyanopyrrolide), the class of choline amino acid ionic liquids (e.g., choline prolinate), the class of 1,3-dialkylimidazolium boron tetrafluorides (e.g., 1-butyl-3-methylimidazolium boron tetrafluoride), and the class of 1,3-dialkylimidazolium phosphorus tetrafluorides (e.g., 1-butyl-3-methylimidazolium phosphorus tetrafluoride), wherein the term alkyl is independently, in each instance, selected from linear or branched alkyl groups containing 1-12 carbon atoms (or more particularly, 1-6, 1-4, or 1-3 carbon atoms). A range of possible carbon-capturing ionic liquids are described in W. F. Elmobarak et al., Fuel, 344, July 2023, 128102, the contents of which are herein incorporated by reference. Any such ionic liquid may be included in the core of the carbon capture particle described herein.

[0023] In a second set of embodiments, the liquid sorbent in the core is or includes a deep eutectic solvent (DES), which are well known in the art. For purposes of the present invention, the DES should have the ability to be reactive with carbon dioxide. As well known, a DES is a liquid formed from two precursors which, when complexed with each other, form a substance having a substantially lower melting point than the precursors. The DES may be a Type I, Type II, or Type III DES solvent. A range of possible DES solvents with carbon capture ability are described in J. Ruan et al., Green Chem., 25, 8328-8348, 2023, the contents of which are herein incorporated by reference. In some embodiments, the DES is a glycerol-based deep eutectic solvent, such as described in M. K. AlOmar et al., Journal of Molecular Liquids, 215, 98-103, March 2016, the contents of which are herein incorporated by reference. The glycerol-based DES may be composed of, for example, glycerol combined with an ammonium or phosphonium salt. Alternatively, the DES may contain monoethanolamine, diethanolamine, ethylene diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and/or tetraethylene glycol in combination with an ammonium or phosphonium salt, wherein urea may or may not be included as an additional component. In some embodiments, the salt component of the DES can be or include any of the aforementioned ionic liquids. Some particular examples of DES solvents include choline chloride-monoethanolamine, glyceline, reline, piperazine glyceline, tetraethylenepentamine chloride-thymol, choline chloride-ethanolamine-urea, methyltriphenylphosphonium bromide-ethylene glycol, methyltriphenylphosphonium bromide-glycerol, methyltriphenylphosphonium bromide-diethylene glycol, tetrapropylammonium chloride-ethanolamine, 1-ethyl-3-methylimidazolium 2-cyanopyrrolide-ethylene glycol, and choline prolinate ethylene glycol.

[0024] In a third set of embodiments, the liquid sorbent in the core is or includes an alkylamine solvent. The alkylamine may, in some embodiments, be a hydrophobic amine that can dissolve in an organic (non-aqueous) solvent (NAS) or low-aqueous solvent (LAS). In other embodiments, the alkylamine can dissolve in an aqueous solution. The alkylamine typically has the formula NR.sup.dR.sup.eR.sup.f, wherein R.sup.d, R.sup.e, and R.sup.f are selected from H and hydrocarbon groups containing one or more carbon atoms, wherein one, two, or all three of Rd, Re, and Rf are selected from hydrocarbon groups. The hydrocarbon groups may independently contain 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms and may or may not contain one or more heteroatoms selected from O, N, and S. In different embodiments, the hydrocarbon groups contain 1-12, 1-6, 1-4, 1-3, 2-12, 2-6, 2-4, or 2-3 carbon atoms. The hydrocarbon groups may be linear or branched alkyl or alkenyl groups or saturated or unsaturated monocyclic or bicyclic groups. Some examples of hydrocarbon groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl, isohexyl, n-octyl, 2-ethylhexyl, 2-ethyloctyl, n-decyl, n-dodecyl, cyclohexyl, phenyl, pyridyl, and tolyl groups. Some examples of such alkylamines include triethylenetetramine, polyethyleneimine, tetraethylenepentamine, diethylenetriamine, trimethylpropane-1,3-diamine, N-(2-ethoxyethyl)-N,N-diisopropylethane-1,2-diamine, N-(2-ethoxyethyl-3-morpholinopropan-1-amine, and N-isobutyl-3-morpholinopropan-1-amine.

[0025] The term alkylamine, as used herein, may also include alkanolamines. Alkanolamines are well known in the art for carbon dioxide capture. Some examples of alkanolamines include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diglycolamine (DGA), methyldiethanolamine (MDEA), diisopropanolamine, 2-amino-2-methyl-1-propanol, 2-(piperidin-2-yl)ethanol, 2-(diethylamino)ethanol (DEEA), N-butyldiethanolamine (BDEA), N-t-butyldiethanolamine (t-BDEA), and N-ethyldiethanolamine (EDEA).

[0026] The shell of the carbon capture composite particle encapsulates (surrounds) the core and contains a multiplicity of hydrophobic-coated oxide particles (HCOPs), wherein gas-permeable spacings (pores or gaps) are present between the HCOPs. The HCOPs generally have a size within a range of 1-1000 nm. In more particular embodiments, the HCOPs have a size in a range of 1-500 nm, 1-250 nm, 1-100 nm, 1-50 nm, 1-20 nm, 1-10 nm, 5-1000 nm, 5-500 nm, 5-250 nm, 5-100 nm, 5-50 nm, 5-20 nm, 5-10 nm, 10-1000 nm, 10-500 nm, 10-250 nm, 10-100 nm, 10-50 nm, 10-20 nm, 50-1000 nm, 50-500 nm, 50-250 nm, or 50-100 nm. As the HCOPs occupy only a portion of the total volume of the carbon capture composite particle, the carbon capture composite particle is necessarily larger than the HCOPs, e.g., 0.01-1000 microns (or, more particularly, 0.01-100 microns, 0.01-50 microns, 0.1-1000 microns, 0.1-100 microns, 0.1-50 microns, 1-1000 microns, 1-500 microns, 1-100 microns, or 1-50 microns). The spacings between HCOPs typically have a minimum size of 0.1, 0.2, 0.5, or 1 nm and a maximum size 2, 5, 10, 50, 100, 200, 500, or 1000 nm, or spacings in a range bounded by any two of these values, e.g., 0.1-1000 nm, 0.1-500 nm, 0.1-200 nm, 0.1-100 nm, 0.1-10 nm, 0.1-1 nm, or 0.1-0.5 nm. The HCOPs are present in an amount of precisely or about 30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, or 90 wt % by weight of the carbon capture particle. The HCOPs may alternatively be present in an amount within a range bounded by any two of the foregoing values, e.g., 30-90 wt %, 40-80 wt %, or 50-70 wt % of the carbon capture particle.

[0027] The HCOPs have a main group or transition metal oxide inner portion encapsulated by a coating of hydrophobic molecules. The main group metal may be any of the elements in Groups 13-15 of the Periodic Table. The transition metal may be any of the elements in Groups 3-12 of the Periodic Table and may be a first row, second row, or third row transition metal. The metal oxide may or may not include hydroxide (OH) groups. Some examples of main group oxide compositions for the inner of the HCOPs include SiO.sub.2 (i.e., silica, e.g., glass or ceramic), B.sub.2O.sub.3, Al.sub.2O.sub.3 (alumina), Ga.sub.2O.sub.3, SnO, SnO.sub.2, PbO, PbO.sub.2, Sb.sub.2O.sub.3, Sb.sub.2O.sub.5, and Bi.sub.2O.sub.3. Some examples of transition metal oxide compositions include Sc.sub.2O.sub.3, TiO.sub.2 (titania), TiO(OH).sub.2, MoO.sub.3, V.sub.2O.sub.5, Cr.sub.2O.sub.3, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, FeO, FeO(OH), CO.sub.2O.sub.3, Ni.sub.2O.sub.3, NiO, CuO, Cu.sub.2O, MnO.sub.2, ZnO, Y.sub.2O.sub.3 (yttria), ZrO.sub.2 (zirconia), NbO.sub.2, Nb.sub.2O.sub.5, RuO.sub.2, PdO, Ag.sub.2O, CdO, HfO.sub.2, Ta.sub.2O.sub.5, WO.sub.3, WO.sub.2, Ag.sub.2O, and PtO.sub.2, or a mixed oxide composition containing any two or more of the above. In some embodiments, any one or more of the foregoing species of oxide composition are excluded from the shell. In some embodiments, the shell may include or exclusively contain hydrophobized particles having a magnetic oxide composition (e.g., Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, or FeO), in which case the shell of hydrophobized magnetic oxide particles can serve as the HCOP and magnetic particles, thereby not requiring the presence of other magnetic particles. In some embodiments, the shell is composed of magnetic oxide particles in admixture with non-magnetic oxide particles, such as silicon dioxide. In some embodiments, the oxide in the HCOP is non-magnetic or does not contain iron. In particular embodiments, the oxide in the inner portion of the HCOP is or includes silica (SiO.sub.2). In other particular embodiments, the oxide in the inner portion of the HCOP is or includes a silicate or an aluminosilicate (i.e., zeolites or clays). The zeolite may be an H-type zeolite or metal ion-exchanged zeolite. Some examples of zeolites include HZSM-5, H-Y, H-Beta, SAPO-34, and SSZ-13 types of zeolites. Notably, the oxide inner portion may or may not include elements other than main group or transition metal elements, e.g., alkaline earth and/or lanthanide elements.

[0028] Any of the oxide inner portions exemplified above are encapsulated by a coating of hydrophobic molecules to result in HCOPs that encapsulate the liquid sorbent core of the carbon capture particles. In typical embodiments, HCOPs are produced by reacting an oxide particle (e.g., silica or titania particles) with trialkoxyalkylsilane (e.g., trimethoxy or triethoxyoctylsilane, i.e., TEOS) molecules in the presence of a base or acid to induce covalent bonding of the trialkoxyalkylsilane to the surface of the oxide particle. Oxide particles may alternatively be reacted with an alkylphosphonic acid (e.g., hexylphosphonic acid) or alkylcarboxylic acid (e.g., docosanoic acid) to bond alkyl groups to the surface of the oxide particles to result in HCOPs. The resulting coated oxide particles are thus alkyl-coated oxide particles.

[0029] In some embodiments, the carbon capture composite particle further includes magnetic nanoparticles embedded in the core and/or shell of the carbon capture particle. The individual magnetic particles are typically ferromagnetic or ferrimagnetic, leading to bulk paramagnetism or superparamagnetism. More typically, the magnetic particles have an iron-containing composition, such as an Fe.sub.3O.sub.4 (magnetite) composition. Other magnetic compositions include Fe.sub.2O.sub.3 (maghemite), Fe, Co, Nd, NdFeB, or any other ferromagnetic or ferrimagnetic material. The magnetic nanoparticles generally have a size within a range of 1-500 nm. In more particular embodiments, the magnetic nanoparticles have a size in a range of 1-250 nm, 1-100 nm, 1-50 nm, 1-20 nm, 1-10 nm, 5-500 nm, 5-250 nm, 5-100 nm, 5-50 nm, 5-20 nm, 5-10 nm, 10-500 nm, 10-250 nm, 10-100 nm, 10-50 nm, 10-20 nm, 50-500 nm, 50-250 nm, or 50-100 nm. The magnetic particles can be uncoated (typically, native OH-functionalized) or hydrophobized (e.g., oleic acid coated) magnetic particles.

[0030] The carbon capture core-shell particles described above can be produced by any method in which a liquid sorbent can be integrally mixed with hydrophobic oxide particles and optionally magnetic particles until a visually uniform homogeneous and free-flowing powder is formed. In typical embodiments, the carbon capture core-shell particles are produced by grinding (either manually or by machine) a liquid sorbent and hydrophobic oxide particles until a visually uniform homogeneous and free-flowing powder is formed. This may also be achieved using a blender or an emulsifier to combine the components.

[0031] In another aspect, the present disclosure is directed to a method for capturing carbon dioxide by use of any of the carbon capture composite (CCC) particles described above. In the method, the CCC particles are contacted with a gaseous source containing carbon dioxide. The gaseous source can be, for example, air, waste gas from an industrial or commercial process, flue gas from a power plant, exhaust from an engine, or sewage or landfill gas, any of which may be raw or cleansed upon contact with the carbon capture particles. The gas-permeable spacings in the shell of the CCC particles permit passage of the gaseous source to the liquid sorbent in the core. Upon contact, the gaseous source infiltrates into the gas-permeable spacings in the shell of the CCC particles and migrates through the shell to make contact with the liquid sorbent in the core of the CCC particles.

[0032] The liquid sorbent, such as any of those described above, typically reacts with carbon dioxide to form a carbamate or an ion pair bond of the formula:

##STR00001##

wherein R.sup.a, R.sup.b, and R.sup.x are selected from H and hydrocarbon groups as described above, e.g., containing 1-12 carbon atoms (e.g., methyl and any of the other hydrocarbon groups described above), wherein at least one of R.sup.a, R.sup.b, and R.sup.c is H; the dashed double bond represents the presence or absence of a double bond (i.e., if the dashed double bond is absent, the single bond to R.sup.c remains), and the dashed single bond represents the presence or absence of R.sup.c, wherein R.sup.c is present only if the double bond is not present (or conversely, R.sup.c is absent if the double bond is present); X.sup.m- is a carbonate (CO.sub.3.sup.2-) or bicarbonate (HCO.sub.3.sup.) anion, with m being 1 for bicarbonate and 2 for carbonate; and n is an integer of 1 or 2, provided that nm=2.

[0033] More specifically, the ion pair bond has any of the following two formulas:

##STR00002##

[0034] The method may further include a step of regenerating the carbon capture particles after they form a complex with carbon dioxide. In the method for regenerating a carbon dioxide sorbent material, carbon capture particles containing a sorbent-CO.sub.2 complex containing CO.sub.2 in the form of a carbamate, bicarbonate, or carbonate, as described above, are exposed to microwave (MW) or radiofrequency (RF) radiation. Upon exposure to the radiation, the sorbent-CO.sub.2 complex reverts to the original active sorbent along with release of carbon dioxide, wherein the released carbon dioxide may be pressurized and stored for later use in a carbon dioxide conversion process (to produce a valuable commodity chemical), oil enhanced recovery, or a dry ice manufacturing process. Typically, the regeneration process does not expose the carbon capture complexed particles to direct heating. Although the MW or RF radiation may produce some amount of residual heat, the primary mechanism by which the MW or RF radiation induces regeneration is by electromagnetic-induced rearrangement of the molecular bonds in the liquid-CO.sub.2 complex. In some embodiments, the regenerated capture carbon particles are re-used to capture CO.sub.2 and form a complex therewith. The re-used carbon capture particles may then be regenerated, and the cycle continued.

[0035] In another aspect, the present disclosure is directed to an apparatus for regenerating a sorbent liquid in a sorbent-CO.sub.2 complex as described above. The apparatus includes the following components: (i) a column for housing the sorbent-CO.sub.2 complex and through which a gas can flow, wherein the column is partially or completely microwave-transparent or radiofrequency-transparent to permit microwave or radiofrequency radiation to be transmitted through the column to contact the sorbent-CO.sub.2 complex and (ii) a device for generating MW or RF radiation. In some embodiments, the column is entirely MW-transparent or RF-transparent. In some embodiments, the MW-transparent or RF-transparent window or column is constructed of poly(tetrafluoroethylene) (PTFE). In some embodiments, the column includes a MW-transparent or RF-transparent window through which MW or RF radiation can be transmitted to contact the sorbent-CO.sub.2 complex. Typically, the column is within an enclosed chamber in which MW or RF is generated. The enclosed chamber may be, for example, a MW or RF cavity. The apparatus is also typically fitted with an inlet and outlet for purging of gases in the column. The top and bottom of the column typically contains glass frits which allow for packing of the material between the inlet and outlet while permitting the gas to pass through the frit to provide an even distribution of gas flow and preventing particles from being released at the outlet.

[0036] Examples have been set forth below for the purpose of illustration and to describe certain specific embodiments of the invention. However, the scope of this invention is not to be in any way limited by the examples set forth herein.

EXAMPLES

Overview

[0037] In the following experiments, carbon capture particles were prepared by a method shown schematically in FIG. 1. Although an ionic liquid (specifically, 1-ethyl-3-methylimidazolium 2-cyanopyrrolide) is depicted as the CO.sub.2-reactive sorbent, any of the reactive ionic liquids, deep eutectic solvents, or alkylamines described above can be instead used. Moreover, although hydrophobic silica particles are depicted, any of the hydrophobic oxide particles described above (e.g., titania or zirconia) can instead be used.

Experimental Methods

Functionalized Silica Support-C.sub.8SiO.sub.2

[0038] 10 g of SiO.sub.2, Cabosil M-5 (1.5 mmol OH/g) particles (5-50 nm; agglomerated >100 nm) surface area of 200 m.sup.2/g, was suspended in a solution of 200 mL of EtOH, 11 mL NH.sub.3(aq), and triethoxy (octyl) silane (C.sub.8TEOS) at 0.3 mol equivalent to OH on the silica. The suspension was stirred overnight at room temperature, after which the liquid was removed via drying on a hotplate at 50 C. The resulting solid was ground via mortar and pestle to break up large clumps and then dried under vacuum at 50 C. overnight.

Ionic Liquid [EMIM][2CNpyr] Synthesis

[0039] [EMIM][2CNpyr] was synthesized by exchanging [EMIM][Br] to [EMIM][OH] with an anion exchange resin column followed by metathesis with H-2CNPyr. Here the column was prepared by adding 40 g of Amberlite IRN-78 resin to a chromatography column, rinsing with 200 mL H.sub.2O, and conditioning with 250 mL of 1 N NaOH. The column was allowed to drip slowly for 1 hr, followed by neutralizing it to pH of 7 with H.sub.2O. A 50/50 H.sub.2O/MeOH (v/v) was then flowed through the column followed by pure methanol (MeOH). 2 g of [EMIM] [Br] (10.4 mmol) was dissolved in a minimal amount of MeOH added to the column and eluted with MeOH slowly. Bromide removal was confirmed by a silver nitrate test. 1 g (10.8 mmol, 1.04 excess) of H-2CNPyr was added to the [EMIM][OH] MeOH solution and mixed. Solvent was removed by rotary evaporation followed by drying under vacuum at 50 C.

Composites of Powdered Sorbents

[0040] Powdered liquids were fabricated through grinding the support, i.e., C.sub.8SiO.sub.2 with desired weight loading of sorbent (i.e., amine, ionic liquid or deep eutectic or polyethyleneimine, PEI) [EMIM][2CNPyr], with a mortar and pestle until a visually uniform, homogeneous free-flowing powder was formed (60 seconds).

[0041] For composites containing magnetic nanoparticles, the desired weight loading of magnetic nanoparticles (commercially obtained Fe.sub.3O.sub.4, Fe.sub.3O.sub.4-silane coated, Fe.sub.3O.sub.4OH functionalized, and Fe.sub.3O.sub.4-oleic acid coated) was added to the sorbent (0-1 wt %) then this was ground with the C.sub.8SiO.sub.2 as above.

Breakthrough Measurements and Regeneration

[0042] Breakthrough measurements with MW regeneration were performed using a custom build apparatus depicted in FIG. 2. Commercial flow controllers with a range of 0-1.2 L min-1 were used to control flow rate, and a commercial infrared gas analyzer (IRGA) was used to measure CO.sub.2 concentration and flowrate. The composite materials were pretreated at 60 C. under vacuum for 1 hr and cooled under argon. 400 mg of sample was packed into the column and sealed on either end with a glass fiber filter. To maintain the integrity of the glass fiber filters, a glass frit was cut to size and used to support the filter. Pure N.sub.2 was run through the column at room temperature to remove any remaining air, CO.sub.2, and moisture during loading, until the measured CO.sub.2 concentration was 0 ppm and regulated for a 200 mL min.sup.1 flow rate. The flow was then diverted to bypass and feed gas was switched to 412 ppm CO.sub.2 in N.sub.2. Upon stabilization at the expected concentration for 1 min, the flow was switched back to the column for absorption. The experiment was stopped by switching back to the bypass after CO.sub.2 concentration returned to the feed concentration. To study humid conditions, the feed was bubbled through water in a stainless-steel humidifier following the flow controller. Under MW desorption conditions, the feed gas was switched to pure N.sub.2 and sent to the column until stabilization at 0 ppm for 1 min. The MW (2.45 GHZ) was activated at the desired power for 1 hour.

[0043] Breakthrough varying humid conditions were measured with the same equipment and sample preparation. Using the MFCs to maintain a flowrate of 100 sccm, the CO.sub.2 was fed through the cell containing water to create a humid stream, which was then mixed with a dry line of the same gas at the desired ratio to achieve the desired % RH. A steady pressure drop of 85 kPa was observed throughout the experiments. To prevent water condensation in the column due to pressure drop, 0%, 13%, 21%, and 35% RH were measured, corresponding to 0, 0.25, 0.5, and 0.75 contribution from the humid stream (1 00% RH @ 25 C.=31.6 mbar, 31.6/1.85=17.3 mbar or 55% RH @ 25 C.). The humidifier was also kept at room temperature (21 C.).

[0044] Capacity for CO.sub.2 and H.sub.2O were calculated via Equation 1:

[00001]$z_i=\frac{\left({}_0^{t}F\left(1-C_i/C_{i,0}\right)\mathrm{dt}\right)C_{i,0}}{{\stackrel{}{V}}_{\mathrm{STP}}.Math.W}$

where z.sub.i is the loading of component i in the sorbent, t is time in min, F represents the feed flow rate in sccm, C.sub.i and C.sub.i,0 are the concentrations of component i (in ppm) in the feed and exit streams, respectively, {circumflex over (V)}.sub.STP is the molar volume of an ideal gas at STP (22.4 cm.sup.3/mmol), and W is the weight of the sample in grams. Breakthrough capacity was calculated by setting t to the breakthrough time, t.sub.BT, when the effluent CO.sub.2 concentration reached 5% of the feed concentration, and final capacity was calculated setting t to the final time, t.sub.f, when the effluent CO.sub.2 concentration reached 99% of the feed concentration.

[0045] While there have been shown and described what are at present considered the preferred embodiments of the invention, those skilled in the art may make various changes and modifications which remain within the scope of the invention defined by the appended claims.