WO2024159165A1 - Preparation of magnesium oxide and carbon dioxide capture using magnesium: oxide - Google Patents

Preparation of magnesium oxide and carbon dioxide capture using magnesium: oxide Download PDF

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Publication number
WO2024159165A1
WO2024159165A1 PCT/US2024/013214 US2024013214W WO2024159165A1 WO 2024159165 A1 WO2024159165 A1 WO 2024159165A1 US 2024013214 W US2024013214 W US 2024013214W WO 2024159165 A1 WO2024159165 A1 WO 2024159165A1
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Prior art keywords
mgo
magnesium oxide
oxide particles
composition
mesoporous magnesium
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PCT/US2024/013214
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French (fr)
Inventor
Maohong Fan
Sam TOAN
Lei Wang
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University Of Wyoming
The Regents Of The University Of Minnesota
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Publication of WO2024159165A1 publication Critical patent/WO2024159165A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/62—Carbon oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/81—Solid phase processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/96—Regeneration, reactivation or recycling of reactants
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/02—Magnesia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/402—Alkaline earth metal or magnesium compounds of magnesium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/60—Inorganic bases or salts
    • B01D2251/602—Oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
    • B01D2252/20—Organic absorbents
    • B01D2252/204—Amines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F5/00—Compounds of magnesium
    • C01F5/02—Magnesia
    • C01F5/06—Magnesia by thermal decomposition of magnesium compounds
    • C01F5/08—Magnesia by thermal decomposition of magnesium compounds by calcining magnesium hydroxide
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

  • Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO 2 absorption, CO 2 desorption, and/or CO 2 capture processes. BACKGROUND [0003] Carbon dioxide (CO2) is a primary greenhouse gas that contributes greatly to global warming, owing to the excessive emissions from the combustion of fossil fuels.
  • Carbon capture, utilization, and storage is the mature technology that can be carried out to alleviate the CO 2 discharge, which is urgently needed for achieving the goals set in the Paris climate Accord.
  • Amine-based CO 2 absorption is a potentially cost- effective option for capturing CO 2 from gas streams (e.g., flue gas) and the atmosphere.
  • CO2 capture is critical because of its increasing importance as a resource for material and fuel synthesis.
  • a fundamental challenge of chemisorption-based technologies is the slow absorption and desorption reaction kinetics when CO2 desorption reaches temperatures greater than 100°C.
  • Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO2 absorption, CO2 desorption, and/or CO2 capture processes.
  • embodiments of the present disclosure enable synthesis of mesoporous magnesium oxide (MgO) nanoparticles in an efficient and scalable manner via precipitation and calcination at various temperatures.
  • the surface structure of the MgO can be nonstoichiometric due to its distinctive shape, which may include several surface hydroxyl groups and lattice defects from its calcination process. Strong catalytic activity can be provided by oxygen vacancies.
  • the MgO nanoparticles show significantly improved breakthrough times, increased absorption capacity, and increased maximum CO2 desorption rate. Further, the MgO NPs can maintain steady efficiency for CO2 absorption and desorption even after repeated usage with no discernible decline in the catalytic impact of MgO.
  • a process for forming mesoporous magnesium oxide particles includes forming a mixture comprising a magnesium source and a templating agent in a liquid. The process further includes introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles. The process further includes separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles. The process further includes calcining the as-synthesized form of the mesoporous magnesium oxide particles under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles.
  • a process for forming mesoporous magnesium oxide particles includes forming a mixture comprising a magnesium source and a templating agent in a liquid. The process further includes introducing an aqueous base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles, the aqueous base comprising an alkali metal carbonate. The process further includes separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles.
  • the process further includes calcining the as- synthesized form of the mesoporous magnesium oxide particles at a temperature that is from about 450°C to about 1200°C to form a calcined form of the mesoporous magnesium oxide particles, the calcined form of the mesoporous magnesium oxide particles having a specific surface area that is from about 100 m 2 g –1 to about 800 m 2 g –1 .
  • a process for capturing carbon dioxide (CO2) is provided. The process includes introducing or contacting a composition with a gas stream comprising CO 2 , the composition comprising mesoporous magnesium oxide particles described herein.
  • a process for capturing carbon dioxide (CO 2 ) from a gas stream includes introducing a gas stream comprising CO 2 with a composition under absorption conditions, the composition comprising: an organic amine; calcined mesoporous magnesium oxide particles having a specific surface area that is from about 100 m 2 g –1 to about 800 m 2 g –1 ; and optionally water.
  • the process further includes forming a CO2-enriched composition.
  • a composition for absorbing or desorbing carbon dioxide (CO 2 ) is provided.
  • the composition includes an organic amine, and magnesium oxide.
  • a process for making a composition for absorbing or desorbing carbon dioxide (CO 2 ) includes ultrasonically treating a mixture comprising MgO particles, organic amine, and water; and optionally introducing an additive to the mixture to form a composition for absorbing or desorbing carbon dioxide.
  • a process for capturing carbon dioxide (CO 2 ) from a gas stream is provided. The process includes introducing a gas stream with a composition described herein under absorption conditions, the gas stream comprising CO 2 . The process further includes forming a CO2-enriched composition. In some embodiments, at least a portion of the composition is ultrasonically pretreated.
  • a process for desorption of carbon dioxide (CO2) from a CO2-enriched composition includes heating a CO2-enriched composition under desorption conditions, the CO 2 -enriched composition comprising: an organic amine, an ion thereof, or a combination thereof; magnesium oxide (MgO); and optionally water, an ion thereof, or a combination thereof.
  • the process further includes separating CO 2 from the CO 2 -enriched composition to form a CO 2 -depleted composition.
  • a process for capturing carbon dioxide (CO2) from a gas stream is provided. The process includes contacting the gas stream with a composition described herein, under absorption conditions, in an absorption unit to form a CO2-enriched composition, the gas stream comprising CO2.
  • the process further includes passing the CO 2 -enriched composition to a desorption unit, and heating at least a portion of the CO 2 - enriched composition in the desorption unit.
  • the process further includes separating CO 2 from the CO 2 -enriched composition to form a CO 2 -depleted composition.
  • the process further includes regenerating the composition from at least a portion of the CO 2 -depleted composition, recycling at least a portion of the CO2-depleted composition to the absorption unit, or both.
  • a process for forming magnesium oxide particles is provided. The process includes forming a mixture comprising a magnesium source, a templating agent, a base, and a solvent.
  • FIG. 1 is a schematic diagram of an example experimental setup for carbon dioxide (CO2) absorption and desorption experiments according to at least one embodiment of the present disclosure.
  • FIG. 2 shows exemplary X-ray diffraction (XRD) patterns of example MgO products calcined at temperatures ranging from about 500°C to about 1,100°C according to at least one embodiment of the present disclosure.
  • FIG. 3A is an exemplary transmission electron microscopy (TEM) image of example products calcined at about 500°C (MgO-500 particles) according to at least one embodiment of the present disclosure.
  • FIG. 3B is an exemplary scanning transmission electron microscopy (STEM) image of example MgO-500 particles according to at least one embodiment of the present disclosure.
  • FIG. 3C-3F are exemplary X-ray energy-dispersive spectroscopy (XEDS) images of example MgO-500 particles according to at least one embodiment of the present disclosure.
  • FIG. 3G is an exemplary TEM image of example products calcined at about 700°C (MgO-700 particles) according to at least one embodiment of the present disclosure.
  • FIG. 3H is an exemplary STEM image of example MgO-700 particles according to at least one embodiment of the present disclosure.
  • FIGS. 3I-3L are exemplary XEDS images of example MgO-700 particles according to at least one embodiment of the present disclosure.
  • FIG. 3G is an exemplary TEM image of example products calcined at about 700°C (MgO-700 particles) according to at least one embodiment of the present disclosure.
  • FIG. 3H is an exemplary STEM image of example MgO-700 particles according to at least one embodiment of the present disclosure.
  • FIGS. 3I-3L are exemplary XEDS images of example Mg
  • FIG. 3M is an exemplary TEM image of example products calcined at about 900°C (MgO-900 particles) according to at least one embodiment of the present disclosure.
  • FIG. 3N is an exemplary STEM image of example MgO-900 particles according to at least one embodiment of the present disclosure.
  • FIGS. 3O-3R are exemplary XEDS images of example MgO-900 particles according to at least one embodiment of the present disclosure.
  • FIG. 3S is an exemplary TEM image of example products calcined at about 1,100°C (MgO-1100 particles) according to at least one embodiment of the present disclosure.
  • FIG. 3T is an exemplary STEM image of example MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIGS. 3U-3X are exemplary XEDS images of example MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG. 4A shows exemplary data for nitrogen (N2) absorption-desorption isotherms for example MgO-700 particles, MgO-900 particles, and MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG.4B shows exemplary data for the pore size distributions of example MgO- 700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG. 4A shows exemplary data for nitrogen (N2) absorption-desorption isotherms for example MgO-700 particles, MgO-900 particles, and MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG.4B shows exemplary data for the pore size distributions of example MgO- 700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present
  • FIG. 5A shows exemplary survey X-ray photoelectron spectroscopy (XPS) spectra of example MgO-700 particles, example MgO-900 particles, and example MgO- 1100 particles according to at least one embodiment of the present disclosure.
  • FIG. 5B shows exemplary high-resolution XPS spectra of the Mg 2p peak of example MgO-700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG.5C shows exemplary high-resolution XPS spectra of the Mg O 1s peak of example MgO-700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG.6 shows exemplary data for the temperature programmed desorption CO2 (TPD-CO 2 ) profiles for example MgO-700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure. Also shown are pictorial representations of example CO 2 absorbed species over weak basic sites, medium basic sites, and strong basic sites according to at least one embodiment of the present disclosure.
  • FIG.7A is a pictorial representation of major reaction pathways of CO2 capture of a 20 wt% MEA solution without MgO particles according to at least one embodiment of the present disclosure.
  • FIG.7B is a pictorial representation of major reaction pathways of CO 2 capture of a 20 wt% MEA solution with example MgO particles according to at least one embodiment of the present disclosure.
  • FIG. 8A is exemplary data showing the effects of example catalysts (MgO particles) on the CO2 absorption quantity and (Cin-Cout)/Cin of a 20 wt% monoethanolamine (MEA) solution catalyzed by 2% MgO-700 particles, MgO-900 particles, or MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG. 1A monoethanolamine
  • FIG. 8B is exemplary data showing the effects of example catalysts (MgO particles) on the CO 2 desorption rate of a 20 wt% MEA solution catalyzed by 2% MgO- 700 particles, MgO-900 particles, or MgO-1100 particles according to at least one embodiment of the present disclosure.
  • FIG. 8C is exemplary data showing the effects of example catalysts (MgO particles) on the CO2 absorption and desorption capacity of a 20 wt% MEA solution catalyzed by 2% MgO-700 particles, MgO-900 particles, or MgO-1100 particles according to at least one embodiment of the present disclosure. (Error bars represent standard deviations from three independent experiments.) [0043] FIG.
  • FIG. 9A is exemplary data showing the effects of example catalysts (MgO particles) on CO 2 absorption amount of a 20 wt% MEA solution catalyzed by 2wt % MgO- 700, MgO-900, or MgO-1100 NPs according to at least one embodiment of the present disclosure.
  • FIG. 9B is exemplary data showing the effects of example catalysts (MgO particles) on CO 2 desorption amount of a 20 wt% MEA solution catalyzed by 2wt % MgO- 700, MgO-900, or MgO-1100 NPs according to at least one embodiment of the present disclosure.
  • FIG. 9B is exemplary data showing the effects of example catalysts (MgO particles) on CO 2 desorption amount of a 20 wt% MEA solution catalyzed by 2wt % MgO- 700, MgO-900, or MgO-1100 NPs according to at least one embodiment of the present disclosure.
  • FIG. 9B is
  • FIG. 10A shows exemplary data for the cyclic performance of a 20 MEA solution without and with example MgO-700 particles on CO2 absorption and desorption according to at least one embodiment of the present disclosure.
  • FIG. 10B is exemplary data showing the stability of MEA/MgO-700 particles CO 2 capture system according to at least one embodiment of the present disclosure.
  • FIGS. 11A, 11B, and 11C show exemplary data for the cyclic performance of example MgO particles demonstrating the effects of the catalysts (MgO particles) on CO 2 absorption amount according to at least one embodiment of the present disclosure.
  • FIGS.11D and 11E show exemplary data for the cyclic performance of example MgO particles demonstrating the effects of the catalysts (MgO particles) on CO2 desorption rate according to at least one embodiment of the present disclosure.
  • FIGS. 11F, 11G, and 11H show exemplary data for the cyclic performance of example MgO particles demonstrating the effects of the catalysts (MgO particles) on CO 2 desorption amount according to at least one embodiment of the present disclosure.
  • FIG. 12A shows exemplary Raman spectra of the CO 2 absorption of MEA aqueous solutions without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure.
  • FIG. 12B shows exemplary Raman spectra of the CO 2 desorption of MEA aqueous solutions without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure. (The indicated times were the periods when samples were taken during desorption tests for Raman spectral analysis. The peak intensities are proportional to the concentration of species in solution.)
  • FIG. 13A shows three-dimensional (3D) surface plots of the Raman intensity of CO 2 absorption without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure.
  • FIG. 13B shows 3D surface plots of the Raman intensity of CO2 desorption without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure.
  • FIG. 14 is a non-limiting graphical representation of selected embodiments of the present disclosure.
  • identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
  • DETAILED DESCRIPTION [0056] Embodiments of the present disclosure generally relate to processes for forming magnesium oxide particles and compositions thereof.
  • the compositions can be aqueous compositions that include an organic amine and magnesium oxide (MgO).
  • MgO organic amine and magnesium oxide
  • the MgO can be in the form particles such as nanoparticles (NPs), though microparticles and macroparticles (among other sizes of particles) are contemplated.
  • the MgO can be mesoporous, having a pore size of about 2 nanometers (nm) to about 50 nm, though other pore sizes such as microporous (pore size of up to about 2 nm) and macroporous (pore size greater than about 50 nm) are contemplated.
  • the MgO surface structure can be nonstoichiometric due to its distinctive shape, and the abundant Lewis base sites provided by oxygen vacancies can promote CO2 capture.
  • the mesoporous MgO nanoparticles (MgO-NPs) can be made using polyethylene glycol (PEG) (e.g., PEG 1500) as a soft template.
  • PEG polyethylene glycol
  • the mesoporous MgO-NPs can accelerate and/or catalyze both sorption and desorption from the organic amine (e.g., monoethanolamine (MEA)) in a superior manner relative to conventional technologies, where industrial applications of conventional CO 2 capture technologies are limited by their slow CO2 sorption and desorption kinetics.
  • adding about 2 wt % MgO-NPs to about 20 wt % MEA can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by about 3,000% and can increase the CO2 absorption capacity within the breakthrough time by about 3,660 %.
  • Fossil fuel-based power generation remains the most reliable method for generating electricity, making up more than 80% of the global energy supply.
  • fossil fuel combustion generates more than 25% of CO 2 emissions, which is linked to global climate change.
  • rapidly deployable flue gas treatment methods that reduce CO2 emission while allowing traditional plants to continue operating are vital to minimizing global climate change while sustaining current energy demands.
  • CO2 makes up a significant portion of the 1 atm pressure fuel gas: 10-15%.
  • post-combustion capture processes will make it possible to convert the gas mixture with relatively high CO 2 concentration into pure gas.
  • the most common post-combustion CO 2 capture methods used in many industrial plants are chemical absorption processes with monoethanolamine (MEA)-based solvents.
  • MEA solvents have been used for over a decade to remove acidic gases from natural gas streams, such as carbon dioxide and hydrogen sulfide.
  • Solvents containing MEA have many advanced properties that make them suitable for capturing CO 2, such as low molecular weight, low solubility for hydrocarbons, high resistance to thermal degradation, a high absorption rate, and low solvent cost.
  • MEA has significant drawbacks that cannot be overlooked. Such drawbacks include a low CO2 absorption ability, amine oxidation-related deterioration, high vapor pressure-related vaporization losses, and high viscosity. Therefore, degradation and corrosion considerations can be prevented by using a relatively low mass fraction, around 20 to 30% amine to H2O.
  • porous catalyst in CO 2 capture systems can enhance CO 2 absorption.
  • materials include metal oxides, metal-organic frameworks (MOF), zeolites, porous polymers, and porous carbons. Nevertheless, finding appropriate materials with desirable characteristics, such as sizeable particular surface area and efficient porosities, and at an affordable cost, remains elusive.
  • the particle size, specific surface area, and bonding ability of nanoparticles with CO 2 can all be factors that can affect the catalytic activities of metal oxide catalysts.
  • the term “magnesium oxide particles” is used interchangeably with the term “catalyst” such that reference to one includes reference to the other.
  • magnesium oxide particles includes reference to both magnesium oxide particles and catalyst, and vice-versa, unless the context indicates otherwise.
  • the magnesium oxide particles can serve to catalyze the absorption of CO 2 to the organic amine and/or catalyze the desorption of CO 2 from the organic amine.
  • one or more components of the composition can exist as ion(s).
  • compositions can include component(s) of the composition, reaction product(s) of two or more components of the composition, a remainder balance of remaining starting component(s), or combinations thereof.
  • Compositions of the present disclosure can be prepared by any suitable mixing process.
  • “composition enriched in CO 2 ”, “carbon dioxide-enriched composition” and “CO2-enriched composition” means that the relative amount (or concentration) of CO2 in a composition after exposure or contact with CO2 is greater than the relative amount of CO2 in a composition before the exposure or contact. For example, if a composition includes 1% CO2 before exposure or contact with CO2, the composition after exposure or contact with CO 2 would include greater than 1% CO 2 .
  • the CO 2 that is sequestered by one or more components of the composition can be in the form of carbonate (CO 3 2 ⁇ ), bicarbonate (HCO 3 ⁇ ), a salt thereof, a reaction product with one or more components of the composition (e.g., a urethane, carbamate, or ion thereof), a physically bound CO2 by electrostatic interactions, for example, Van der Waals forces, or combinations thereof [0069]
  • carbon dioxide-depleted composition” and “CO2-depleted composition” means that the relative amount (or concentration) of CO2 in a composition after desorption or release of CO 2 is less than the relative amount of CO 2 in a composition before the desorption or release.
  • Embodiments of the present disclosure also relate to processes for forming MgO particles, such as those MgO particles described herein.
  • the MgO particles can be nanoparticles.
  • the MgO particles can be mesoporous.
  • the MgO particles can be prepared by a precipitation method using an organic templating agent.
  • a process for forming MgO particles generally includes forming a mixture comprising a magnesium source, a templating agent, a base, and a solvent; and drying and/or calcining the mixture at a temperature of about 450°C to about 1200°C to form magnesium oxide particles.
  • magnesium sources, templating agents, bases, and solvents are described below.
  • a process for forming mesoporous magnesium oxide particles can include forming a mixture comprising a magnesium source and a templating agent in a liquid or liquid medium.
  • the liquid or liquid medium can include any suitable liquid such as water.
  • the magnesium source can be any suitable magnesium source, such as a source comprising magnesium and a ligand and/or a counterion.
  • Counterions and ligands include one or more of halide (for example, I – , Br – , Cl – , or F – ), acetylacetonate (O2C5H7 – ), hydride (H – ), SCN – , NO2 – , NO3 – , N3 – , OH – , oxalate (C2O4 2– ), H2O, acetate (CH3COO – ), O2 – , CN – , OCN – , CNO – ,NH2 – , NC – , NCS – , N(CN)2 – , pyridine (py), ethylenediamine (en), 2,2’- bipyridine (bipy), PPh3, or combinations thereof.
  • halide
  • the templating agent can be any suitable templating agent, such as a glycol.
  • glycols can include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (PEG), polypropylene glycol (PPG), or combinations thereof, among others.
  • the PEG and/or PPG can have any suitable molecular weight such as from about 200 g/mol to about 100,000 g/mol, such as from about 400 g/mol to about 50,000 g/mol, such as from about 500 g/mol to about 3,000 g/mol, such as from about 1,000 g/mol to about 2,000 g/mol, such as from about 1,300 g/mol to about 1,700 g/mol, such as about 1,500 g/mol, though other values are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the templating agent comprises PEG 1500.
  • a weight ratio of the magnesium source to the templating agent in the mixture can be from about agent is from about 10:1 to about 1:1, such as from about 8:1 to about 2:1, such as from about 6:1 to about 4:1, such as about 5:1, though other values are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the process further includes introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles.
  • the base can be any suitable base such as a metal carbonate, such as an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof.
  • Suitable alkali metal carbonates include carbonates of lithium, sodium, potassium, rubidium, cesium, francium, or combinations thereof.
  • Suitable alkaline earth metal carbonates include carbonates of beryllium, magnesium, calcium, strontium, barium, radium, or combinations thereof.
  • a non-limiting example of a base includes sodium carbonate (Na2CO3), lithium carbonate (Li2CO3), potassium carbonate (K2CO3), or combinations thereof, such as sodium carbonate.
  • the base can be in the form of an aqueous solution. [0077] After introducing the base, the resulting mixture is maintained under sufficient conditions to precipitate the as-synthesized form of the mesoporous magnesium oxide particles and optionally occluded templating agent.
  • introducing the base to the mixture to precipitate the as- synthesized form of the mesoporous magnesium oxide particles includes vigorously stirring the mixture while introducing the base to the mixture.
  • Stirring while introducing the base can be performed at suitable rotation speeds, such as from about 50 revolutions per minute (rpm) to about 1,500 rpm, such as from about 100 rpm to about 1,000 rpm, such as from about 200 rpm to about 800 rpm, such as from about 300 rpm to about 700 rpm, such as from about 400 rpm to about 600 rpm, such as from about 450 rpm to about 550 rpm, such as about 500 rpm. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other rotation speeds are contemplated and can be selected based on the ability to mix the components sufficiently.
  • suitable rotation speeds such as from about 50 revolutions per minute (rpm) to about 1,500 rpm, such as from about 100 rpm to about 1,000 rpm, such as from about 200 rpm to about 800 rpm, such as from about 300 rpm to about 700 rpm, such as from about 400 rpm to
  • the mixture can be sonicated or ultrasonicated while introducing the base to the mixture. Vigorous stirring, sonication, or ultrasonication of the mixture can make the surface of the forming metal oxides (e.g., MgO) more uniform and have a larger surface area.
  • the base can be added slowly, such as over a period of about 30 seconds to about 30 minutes, such as from about 1 minute to about 10 minutes, though other periods are contemplated.
  • the precipitate can be separated from liquid remaining in the mixture by an appropriate technique or techniques, for example, by decantation, washing, e.g., with deionized water and/or an alcohol (e.g., ethanol), filtration, drying, or combinations thereof.
  • Drying may take place under sufficient drying conditions, such as in air or an inert atmosphere, e.g., in nitrogen, at a sufficient temperature, for example, from 50°C to about 150°C, such as from about 80°C to about 120° C., for a sufficient time, for example, from 2 hours to 50 hours, such as from about 5 hours to about 20 hours, such as from about 10 hours to about 15 hours, such as about 12 hours, though other periods are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the precipitate containing the as-synthesized form of the mesoporous magnesium oxide particles is calcined under conditions under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles.
  • the calcination conditions can be sufficient to remove residual templating agent, to remove residual water, or combinations thereof.
  • the calcination conditions can include heating the as-synthesized form of the mesoporous magnesium oxide particles at a suitable temperature that is from about 450°C to about 1200°C, such as from about 500°C to about 1100°C, such as from about 600°C to about 1000°C, such as from about 700°C to about 900°C, such as from about 600°C to about 800°C.
  • Calcining can be performed at a temperature (°C) of 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, or 1200, or ranges thereof, though other temperatures are contemplated.
  • a temperature °C
  • Each of the foregoing numbers can be preceded by the word “about,” “at least about,” “less than about,” or “more than about” and any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the calcination conditions can include heating the as-synthesized form of the mesoporous magnesium oxide particles for a suitable time, for example, from about 30 minutes to about 12 hours, such as from about 1 hour to about 5 hours, such as from about 1.5 hours to about 2.5 hours, such as about 2 hours, though other periods are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the calcination conditions can include heating at a suitable temperature for a suitable time period in a suitable atmosphere such as, for example, air.
  • the MgO particles (such as the calcined form of the mesoporous magnesium oxide particles) can have one or more of the following properties: [0082] (a) An average pore diameter (Dp) that is from about 2 nm to about 50 nm, such as from about 2 nm to about 20 nm, such as from about 5 nm to about 15 nm, such as from about 6 nm to about 10 nm, though other average pore diameters are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • Dp An average pore diameter
  • a specific surface area that is from about 100 m 2 g –1 to about 800 m 2 g –1 , such as about 500 m 2 g –1 or less, such as about 250 m 2 g –1 or less, or about 300 m 2 g – 1 or more, such as from about 300 m 2 g –1 to about 800 m 2 g –1 ; or from about 100 m 2 g –1 to about 400 m 2 g –1 , such as from about 150 m 2 g –1 to about 250 m 2 g –1 , though other specific surface areas are contemplated.
  • SBET specific surface area
  • V t A total pore volume (V t ) that is about 2 cm 3 g –1 or less, such as about 1 cm 3 g – 1 or less, such as from about 0.1 cm 3 g –1 to about 1 cm 3 g –1 , such as from about 0.15 cm 3 g –1 to about 0.4 cm 3 g –1 , though other total pore volumes are contemplated.
  • any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the total pore volume is determined as described in the Examples section.
  • An average particle size that is from about 5 nm to about 100 nm, such as from about 8 nm to about 70 nm, such as from about 8 nm to about 10 nm, or from about 15 nm to about 25 nm, or from about 50 nm to about 70 nm, though other values are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • the MgO particles described herein may be used for CO2 capture.
  • Other non-limiting applications can include wastewater treatment and sensors.
  • processes for forming MgO particles described herein can provide high surface area magnesium oxide MgO nanoparticles in a cost-effective manner.
  • the MgO particles formed by processes described herein can be easily recycled after use in, e.g., CO 2 capture or other applications.
  • Example Composition [0088] Embodiments of the present disclosure generally relate to compositions for absorbing and/or desorbing carbon dioxide (CO 2 ).
  • the compositions also referred to as catalyst compositions
  • the compositions generally include a solution or suspension that includes an organic amine and MgO particles.
  • any suitable solvent such as water may be used for dispersing, solubilizing, and/or suspending at least a portion of the MgO particles and/or the organic amine.
  • the MgO particles serve to, e.g., catalyze and/or accelerate absorption, desorption, and/or capture of CO 2 . Properties of the MgO particles are described above. More than one type of MgO particle can be utilized in compositions described herein if desired.
  • the organic amine serves to, e.g., capture and/or absorb CO 2 . More than one organic amine can be utilized with the compositions described herein.
  • the organic amine(s) can include one or more primary, secondary, and/or tertiary organic amine compounds.
  • the one or more primary, secondary, and/or tertiary organic amine compounds can include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), or combinations thereof.
  • the one or more organic amines can include amine-functionalized polymers such as polyethylene amine.
  • the polyethylene amine can include diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA), polyethyleneimine (PEI), or combinations thereof.
  • an amount of MgO particles in compositions described herein can be about 0.1 wt% to about 10 wt%, such as from about 0.5 wt% to about 5 wt%, such as from about 1 wt% to about 3 wt%, such as about 2 wt% based on a total weight of the composition.
  • the amount (wt%) of MgO particles in compositions described herein can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.
  • each of the foregoing numbers can be preceded by the word “about,” “at least about,” “less than about,” or “more than about” and any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range.
  • Other amounts of MgO particles in the composition are contemplated. Combinations of different MgO particles can be utilized. [0092] Any of the foregoing amounts can apply to a single type of MgO particle, the total amount of a combination of MgO particles, or the total amount of all MgO particles present in the composition.
  • the amount of MgO particles used for the compositions can be based on the dry weight of the MgO particles (e.g., the MgO particles without moisture).
  • an amount of organic amine in compositions described herein is about 1 wt% or more and/or about 99 wt% or less, such as from about 5 wt% to about 95 wt%, such as from about 10 wt% to about 90 wt%, such as from about 15 wt% to about 85 wt%, such as from about 20 wt% to about 80 wt%, such as from about 30 wt% to about 70 wt%, based on a total weight of the composition.
  • the amount of organic amine can be from about 5 wt% to about 40 wt%, such as from about 10 wt% to about 35 wt%, such as from about 15 wt% to about 30 wt%, such as from about 20 wt% to about 25 wt%, based on a total weight of the composition.
  • the amount (in wt%) of organic amine in compositions described herein can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 87, 88, 89, 91, 92, 93, 94, 95, 96, 97, 98, or 99, or ranges thereof.
  • the amount (wt%) of organic amine in the composition is about 10 wt% or more, about 15 wt% to about 25 wt%, about 50 wt% or less, or at least about 20 wt%. Any of the foregoing amounts can apply to a single organic amine, the total amount of a combination of organic amines, or the total amount of all organic amines present in the composition. Other amounts of the one or more organic amines in the composition are contemplated.
  • compositions described herein can include any suitable additive.
  • additives include a surfactant, an antifoaming agent, or combinations thereof, among others.
  • the surfactant can serve to minimize agglomeration and sedimentation of MgO nanoparticles in the solution.
  • the antifoaming agent can serve to reduce the amount of bubbles produced by the surfactant, thereby facilitating the process of packing, sampling, and testing the solution.
  • a surfactant e.g., 1-hexadecyl trimethyl ammonium bromide (CTAB, CH3(CH2)15N(CH3)3Br) and/or an antifoaming agent (such as Antifoam 204) can be utilized in compositions described herein comprising the one or more MgO particles, the one or more organic amines, and the solvent (e.g., water).
  • CTAB 1-hexadecyl trimethyl ammonium bromide
  • an antifoaming agent such as Antifoam 204
  • Other surfactants and antifoaming agents are contemplated.
  • An amount of surfactant in compositions described herein can be from about 0.01 wt% to about 1 wt%, such as from about 0.1 wt% to about 1 wt%, such as from about 0.2 wt% to about 0.9 wt%, such as from about 0.3 wt% to about 0.8 wt%, such as from about 0.4 wt% to about 0.7 wt%, such as from about 0.5 wt% to about 0.6 wt%, based on the total weight of the composition.
  • the amount of surfactant in compositions described herein can be greater than 0 wt% and about 0.5 wt% or less, such as about 0.4 wt% or less, such as about 0.3 wt% or less, such as about 0.2 wt% or less, such as about 0.1 wt% or less, based on the total weight of the composition. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other amounts are contemplated.
  • An amount of antifoaming agent in compositions described herein can be from about 0.01 wt% to about 1 wt%, such as from about 0.1 wt% to about 1 wt%, such as from about 0.2 wt% to about 0.9 wt%%, such as from about 0.3 wt% to about 0.8 wt%, such as from about 0.4 wt% to about 0.7 wt%, such as from about 0.5 wt% to about 0.6 wt%, based on the total weight of the composition.
  • the amount of antifoaming agent in compositions described herein can be greater than 0 wt% and about 0.5 wt% or less, such as about 0.4 wt% or less, such as about 0.3 wt% or less, such as about 0.2 wt% or less, such as about 0.1 wt% or less, based on the total weight of the composition. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other amounts are contemplated. The amount of the surfactant and the antifoaming agent can be the same or different.
  • Embodiments of the present disclosure also relate to a process for making a composition for absorbing or desorbing carbon dioxide (CO2).
  • the method generally includes forming a mixture of one or more MgO particles, one or more organic amines, and a solvent (e.g., water).
  • the solvent, the one or more MgO particles, and the one or more organic amines can be mixed by suitable methods.
  • two or more components of the composition can be subjected to sonication or ultrasonication prior to and/or after introducing the third component to the composition.
  • a mixture of solvent and the one or more organic amines can be subjected to sonic treatment or ultrasonic treatment.
  • the sonically- or ultrasonically-treated mixture can be introduced with the one or more MgO particles to form a composition described herein.
  • the resulting mixture can be subjected to sonic treatment or ultrasonic treatment.
  • an additive can be added to the mixture comprising the one or more MgO particles, the one or more organic amines, and the solvent (e.g., water).
  • Additives such as surfactants, antifoaming agents, among others can be used, and are described above.
  • Example Processes for Absorbing and/or Desorbing Carbon Dioxide [0100] Embodiments of the present disclosure also generally relate to processes for absorbing carbon dioxide (CO 2 ), desorbing CO 2 , and/or capturing CO 2 .
  • CO 2 is present in a gas or a gas stream.
  • the gas or gas stream is introduced and/or contacted with a composition described herein, and a CO2-enriched composition is formed.
  • the gas or gas stream can have any suitable amount of one or more gases.
  • the gas or gas stream can include CO2 with one or more other gases such as N2 and/or O2 in any suitable concentrations.
  • a process for absorbing, desorbing, and/or capturing carbon dioxide (CO 2 ) includes contacting/introducing, under absorption conditions, a gas or gas stream with a composition described herein to form a CO 2 -enriched composition. The contact and/or introduction can occur in an absorption unit.
  • the absorption conditions can include various, temperatures, pressures, times, flow rates of the gas (or gas stream) and/or other parameters suitable for absorption.
  • at least a portion of CO2 can be desorbed (e.g., removed) from the CO2-enriched composition under desorption conditions.
  • Such desorption can be performed in a desorption unit.
  • the desorption unit can be the same unit as the absorption unit, except that, e.g., the unit is placed under desorption conditions.
  • the CO 2 -enriched composition can be passed to a separate desorption unit.
  • Desorption conditions can include various temperatures, pressures, times, flow rates of gases into the desorption unit, and/or other parameters suitable for absorption.
  • At least a portion of the composition can be heated in the desorption unit to a temperature of about 20°C or more and/or about a temperature that is less than a boiling point of the solvent (e.g., water), for example, from about 25°C to about 100°C, such as from about 50°C to about 95°C, such as from about 70°C to about 90°C, such as about 85°C or about 90°C. Other temperatures are contemplated.
  • CO 2 is desorbed, removed, or otherwise separated from CO 2 -enriched composition to form a CO 2 -depleted composition.
  • the CO 2 -depleted composition can still contain an amount of CO 2 .
  • a composition described herein can be regenerated from at least a portion of the CO2-depleted composition. Additionally, or alternatively, at least a portion of the CO2-depleted composition can be recycled to the absorption unit.
  • mesoporous MgO NPs with abundant oxygen vacancies were prepared via the co-precipitation-calcination process with PEG 1500 as a soft template and used the resulting MgO produces as catalysts for CO 2 capture.
  • An aqueous MEA solution (20 wt%) was used as the CO2 absorbent. Investigations into how MgO NPs, with various morphologies, basic sites, and oxygen vacancies, affect the kinetic rates of CO2 capture in MEA solution were performed.
  • mesoporous MgO NPs with abundant oxygen vacancies were prepared via the co-precipitation-calcination process with PEG 1500 as a soft template and used the resulting MgO produces as catalysts for CO2 capture.
  • An aqueous MEA solution (20 wt%) was used as the CO2 absorbent. Therefore, investigations into how MgO NPs, with various morphologies, basic sites, and oxygen vacancies, affect the kinetic rates of CO 2 capture in MEA solution were performed 1.
  • Materials and Test Methods 1.1. Materials [0107] Unless otherwise indicated, all raw materials were analytical grade and were used as received. 1.2.
  • Powder X-ray diffraction (XRD) data were obtained using an X-Pert diffractometer (Philip, Holland) with Cu K ⁇ radiation operated at 40 kV and 40 mA.
  • TEM transmission electron microscopy
  • STEM scanning transmission electron microscopy
  • TALOS F200X Thermo Scientific, USA
  • XEDS X-ray energy-dispersive spectroscopy
  • Temperature programmed desorption was performed on an AutosorbiQ apparatus (Quantachrome Instruments, USA) equipped with a thermal conductivity detector (TCD) detector.
  • TPD thermal conductivity detector
  • the samples 60 mg were processed in situ in a 50 mL/min helium (He) flow at 150°C for 30 minutes, then cooled to 50°C.
  • the samples were then exposed to CO2 (20 mL/min) for 120 min at 50°C.
  • the physisorbed CO2 was removed by flushing with a 50 mL/min flow of He for 90 min.
  • TPD was performed in the stream of He at a heating rate of 10°C/min up to 800°C.
  • An example base was prepared by dissolving sodium carbonate (Na2CO3, about 15.9 g) in DI water (about 300 mL). While the magnesium salt solution was vigorously stirred within the rate of 100-1,000 rpm or by sonication, or by ultrasonication, the base was added dropwise over a period from 1-10 minutes.
  • the resulting solution was carefully washed with an appropriate solvent (e.g., ethanol) to separate the precipitate from the liquid, and dried at about 80°C for about 12 hours (h).
  • the as-synthesized MgO NPs were then calcined at a desired temperature (about 500°C, about 700°C, about 900°C, or about 1100°C) for a desired period (about 2 h). Calcination resulted in a calcined form of the MgO NPs.
  • the products were named as MgO-500, MgO-700, MgO-900, and MgO-1100, respectively with reference to the calcination temperature.
  • the production of MgO NPs using the precipitation method can be performed on an industrial scale. Payback Period analysis shows that the investment will experience a profit after three years. Here, if the initial factory is designed to obtain 11,250 kg of MgO NPs daily, the total profit earned is 1,881,184,753 USD in 10 years. 2.2. Compositions for CO 2 Capture [0117]
  • the MgO NPs can be utilized for a variety of applications. One non-limiting application is for CO 2 capture. For CO 2 absorption and desorption experiments, monoethanolamine (MEA) was chosen as an example organic amine.
  • MEA monoethanolamine
  • the MgO-NPs can accelerate and/or catalyze both sorption and desorption from the MEA.
  • the solution can include one or more suitable additives including, for example, a surfactant, an antifoaming agent, or combinations thereof.
  • the surfactant can be utilized to, for example, minimize agglomeration and sedimentation of MgO nanoparticles in the solution.
  • the antifoaming agent can be utilized to depress foaming and bubbles and thereby facilitate the process of packing, sampling, and testing the solution.
  • CTAB 1-hexadecyl trimethyl ammonium bromide
  • Antifoam 204 Sigma, USA
  • the wt% of surfactant and antifoaming agent can be the same. In other examples, the wt% can be different.
  • the resulting MgO solution was stirred using an ultrasonic vibrator (130 ⁇ W, 20 kHz, VCX 130PB, Sonics & Materials Inc., USA) for about 10 ⁇ min to achieve a stable dispersion and suspension.
  • the prepared MgO solution was determined to have good dispersion stability even after sitting for about 24 h or more.
  • CO2 Capture Experiments [0120] Studies on CO 2 absorption and desorption were carried out using the apparatus depicted schematically in FIG. 1.
  • the example CO2 capture experimental setup shown in FIG.1 included the following non-limiting elements: a nitrogen (N2) cylinder 101, a mixed gas cylinder 102, a mass flow controller 103, a thermostatic bath 104, a heater/stirrer 105, a reactor 106, a thermocouple 107, a condenser 108, a desiccator 109, a paperless recorder 110, a gas analyzer 111, and a computer 112.
  • the mixed gas cylinder can include gases such as CO 2 , oxygen (O 2 ), and/or N 2 , among others.
  • a magnetically connected stirrer (e.g., the stirrer of heater/stirrer 105) was coupled to a 250 ml glass reactor (e.g., reactor 106).
  • Each sorption test used about 100 g of MEA diluted to about 20 wt% in water. Both with and without catalyst (MgO) tests were run. The concentration (weight percentage) of nano-MgO catalysts was about 2 wt%.
  • the total gas flow rate for the investigations was about 1,500 mL/min.
  • the gas composition for the investigations was about 10 vol% CO2, about 10 vol% O2, and about 80 vol% N2.
  • the CO2 sorption temperature and sorption time for the investigations were about 25°C, and about 3,600 seconds (s), respectively.
  • CO2 absorption experiments were conducted at room temperature (about 25°C) and atmospheric pressure.
  • a total of about 20 wt% MEA solution was prepared by mixing monoethanolamine (about 20 g) with DI water (about 80 g).
  • Predetermined amounts of the ⁇ 20 wt% MEA and MgO catalyst were added to the reactor under a stirring rate of about 500 rpm.
  • Simulated flue gas that contained about 10 vol% CO 2 , about 10 vol% O 2 , and about 80 vol% N 2 was purchased from Praxair (Danbury, CT, USA).
  • Vögtlin (Monterey, CA, USA) RED-Y mass flow controllers (MFC, for example, mass flow controller 103) were used to control the flow of gases from the gas cylinders (for example, N2 cylinder 101 and mixed gas cylinder 102) to the reactor (for example, reactor 106).
  • MFC mass flow controller 103
  • a total flow of 1,500 mL/min was used to inject the simulated flue gas into the MEA solution.
  • the CO2 concentration at the outlet gas of the reactor was measured with an inline gas analyzer (CAI ZPA, CA, USA) (for example, gas analyzer 111), and a data recording unit (e.g., paperless recorder 110 and computer 112) recorded the measured concentration-time profile.
  • CAI ZPA inline gas analyzer
  • CAI ZPA for example, gas analyzer 111
  • the amount of CO 2 absorbed into the MEA solution was calculated by integrating the recorded CO 2 sorption profiles.
  • the MFC for example, mass flow controller 103 for the mixed gas was closed after completing the absorption step, which took about 3600 s for fresh and cyclic MEA solutions.
  • CO2 desorption was achieved by gradually heating the spent sorbent obtained from the CO2 sorption step to the desired desorption temperature (for example, about 90 °C).
  • the desorbed CO2 was mixed with the carrier gas (N2) at a flow rate of about 500 mL/min.
  • An inline gas analyzer (for example, gas analyzer 111) measured the CO 2 concentration of the gas mixture. CO 2 concentrations in the gas mixture and the corresponding temperatures of the spent MEA solution were recorded over the entire CO 2 desorption process.
  • FIG. 2 shows XRD patterns of the calcined MgO products calcined at temperatures ranging from about 500°C to about 1100°C. All of the products show five distinct diffraction peaks at (111), (200), (220), (311), and (222). These are indexed to the cubic phase of MgO (periclase) (JCPDS No. 87-0652; space group: Fm3m). No other reflections indicating impurities were observed.
  • the crystallite size (D, nm) for MgO products can be determined using the Debye–Scherrer formula of Equation 1: wherein: ⁇ (nm) is the X-ray radiation wavelength; ⁇ is the diffraction peak full width at half maximum (FWHM); and ⁇ is the Bragg diffraction angle. [0127]
  • the estimated crystallite size was determined to be about 9 nm for MgO-500, about 22 nm for MgO-700, about 48 nm for MgO-900, and about 53 nm for MgO-1100. The average crystallite size increased with an increase in calcination temperature.
  • FIGS.3G and 3H the TEM and STEM images of MgO-700—clearly demonstrated that the pore sizes and particle sizes (about 20 nm) can increase with rising temperature.
  • FIGS.3G and 3H the TEM and STEM images of MgO-700—clearly demonstrated that the pore sizes and particle sizes (about 20 nm) can increase with rising temperature.
  • 3G and 3H also indicated that the mesh-like structure can be made up of a network of nanowires.
  • High specific surface area mesoporous nanoparticles have been shown to improve the mass transfer between gas and liquid, resulting in strong CO 2 absorption capacity.
  • the TEM and STEM images of MgO- 900 (FIGS. 3M and 3N) and MgO-1100 (FIGS. 3S and 3T) show that with a further increase in temperature, the holey lamellar structure disappeared, and MgO NPs grew into individual cubic-shaped particles with a particle size of about 50 nm to about 70 nm.
  • STEM HAADF and XEDS analysis were used to further analyze the elemental composition of the example MgO NPs.
  • HAADF images and associated element maps of MgO-500 are shown in FIGS. 3C-3F.
  • the holey lamellar structure’s carbon (C), magnesium (Mg), and oxygen (O) distributions are uniform throughout, as seen in the element maps from the HADDF images.
  • MgO-700, MgO- 900, and MgO-1100 were selected for subsequent investigations.
  • Nitrogen absorption and desorption isotherm curves of example MgO NPs are shown in FIG.4A.
  • the Brunauer–Emmet–Teller (BET) method was used to calculate the specific surface area of the MgO NPs.
  • the Barrett-Joyner-Halenda (BJH) method was used to determine the pore size distribution of the MgO NPs. Selected results are shown in Table 1.
  • Table 1 shows the specific surface area, the pore volume, and the average pore size (average pore diameter) of example MgO NPs estimated from N2 absorption-desorption measurements using BET and BJH methods.
  • S BET refers to BET specific surface area
  • V t refers to total pore volume
  • D p refers to BJH Desorption average pore diameter (4V/A).
  • MgO NPs present typical type IV curves in the range of 0-1.0 relative pressure with a type H3 hysteresis loop. This indicates that the pore structures of the samples were mainly mesopores (about 2 nm ⁇ pore diameter ⁇ about 50 nm).
  • the specific surface area (about 193.3 m 2 g ⁇ 1 ) and total pore volume (about 0.36 m 3 g ⁇ 1 ) of MgO-700 were calculated from the isotherm. These values are higher than those of MgO-900 (about 148.6 m 2 g ⁇ 1 and about 0.26 m 3 g ⁇ 1 ) and MgO-1100 (about 124.3 m 2 g ⁇ 1 and about 0.15 m 3 g ⁇ 1 ).
  • the BJH desorption average pore diameter of MgO-700, MgO- 900, and MgO-1100 were determined to be about 9.2 nm, about 8.0 nm, and 7.6 nm, respectively.
  • FIG. 4B The pore size distribution curves of MgO NPs are shown in FIG. 4B, showing that all investigated samples have mesopores that are between about 2 nm and about 50 nm. Relative to MgO-900 and MgO-1100, MgO-700 has a high proportion of mesopores between about 5 nm and about 15 nm, which is consistent with the TEM images of FIGS. 3G and 3H. While not wishing to be bound by any theory, this finding can be a result of the unique structure of the mesh-like, interconnected MgO structure, whose fundamental components are primary nanoparticles. [0133] XPS was used to determine how the calcination temperature affected the composition of the MgO surface. FIG.
  • FIG.5A shows a XPS survey spectrum associated with MgO-700, MgO-900, and MgO-1100 samples. MgO and O photoelectron peaks were observed, and the three sample peaks were noted as being comparable, which was in agreement with the XRD findings.
  • the Mg 2p peak high-resolution spectra of the three samples are presented in FIG.5B.
  • the Mg 2p spectra of MgO-700 were divided into two peaks at binding energies of about 50.1 eV and about 48.6 eV, corresponding to the existence of Mg(OH)2 and MgO, respectively. Quantitative analysis of the XPS data was utilized to calculate the corresponding molar percentage of Mg species.
  • FIG. 5C shows the high-resolution spectra of O 1s for the three samples.
  • the binding energies of about 528.9 eV and about 530.8 eV were associated with the lattice oxygen of metal oxides (O lat ) and surface-absorbed oxygen species (O ads ), respectively.
  • the ratio of O ads to O lat was utilized to calculate the relative oxygen vacancy concentration.
  • Table 2 also reports the relative oxygen vacancy concentration for the example MgO NPs.
  • CO 2 absorbed species can be bicarbonate, bidentate carbonate, and unidentate carbonate, respectively.
  • the temperature range of about 50 ⁇ to about 175 ⁇ is responsible for weak basic sites and were attributed to the surface hydroxyl groups.
  • the temperature range of about 175 ⁇ to about 400 ⁇ is responsible for medium basic sites and were attributed to the oxygen in Mg 2+ and O 2 ⁇ pairs. Strong basic sites are typically linked to the low coordinate oxide sites at higher temperatures (about 400 ⁇ to about 800°C).
  • CO 2 absorption over weak and medium basic sites may occur as bicarbonate and bidentate carbonate species while CO 2 absorption over strong basic sites may occur as unidentate species.
  • Table 3 shows non-limiting TPD-CO 2 data for the MgO samples.
  • the values under the column headers weak basic sites, medium basic sires, and strong basic sites refer to the CO2 desorption peak area of the various basic sites.
  • TBS refers to total basic sites.
  • the values under the column header TBS refer to the total CO2 desorption peak area of various basic sites.
  • Basic site density is equal to the TBS value divided by the BET surface area value (TBS/BET surface area).
  • Table 3 Weak basic Medium Strong Basic sites Samples TBS sites basic sites basic sites basic sites density MgO-700 1,503 39,841 1,576 42,920 222 MgO-900 975 8,152 1,058 10,185 68.5 MgO-1100 854 6,627 923 8,404 67.6 [0138] The results in Table 3 show three separate MgO sample concentrations of the weak, medium, and strong basic sites differ in the pattern of MgO-700 > MgO-900 > MgO- 1100. Overall, the results presented in Table 3 agree well with the oxygen vacancy concentration order as determined by XPS. [0139] The inset of FIG. 6 shows that MgO-700 has a higher amount of weakly basic sites below about 90 ⁇ .
  • FIG. 7A displays the function of the Zwitterion mechanism.
  • the zwitterion mechanism includes the creation of a carbamate (MEACOO ⁇ ) via a zwitterion intermediate, followed by the hydrolysis-based formation of bicarbonate (HCO 3 ⁇ ).
  • FIG. 7B a possible catalytic sorption- desorption CO 2 mechanism of MgO catalysis is proposed in FIG. 7B.
  • the MgO catalyst can provide Lewis-base sites during the catalysis process.
  • the nitrogen in MEA can eventually break the MgO-CO2 link, which transfers its lone electrons to the remaining MgO-CO 2 bond.
  • MgO NPs can be beneficial in forming a zwitterion during CO 2 sorption and desorption.
  • the as-prepared MgO NPs (MgO-700 NPs, MgO-900 NPs, and MgO-1100 NPs) were evaluated for CO2 absorption at about 298 K (FIGS. 8A-8C). All tests were conducted with a dosage of about 2 wt% MgO NPs. Higher sorption efficiency and quicker CO2 sorption are characteristics of sorbents with longer effective periods.
  • CO2 breakthrough curves are shown in FIG.
  • the sorbent with MgO-700 NPs, MgO-900 NPs, and MgO-1100 NPs can absorb about 158.1 mmol of CO2, about 139.8 mmol of CO2, and about 128.5 mmol of CO2, respectively.
  • the corresponding breakthrough times are about 1550 s, about 1368 s, and about 1276 s, respectively.
  • the process increases the breakthrough time by about 3,000% under the conditions tested.
  • this process is also able to increase the CO 2 absorption capacity within the breakthrough time by about 3,660% under the conditions tested.
  • the MgO NPs catalysts have significantly improved the CO 2 absorption capacity of MEA within the overall capture times.
  • MgO-700 NPs shows the highest absorption capacity (about 212.6 mmol), followed by MgO-900 NPs (about 210.5 mmol), and MgO-1100 NPs (about 207.5 mmol) under the conditions tested.
  • the amount of CO 2 absorbed without using the MgO NPs is about 160.7 mmol.
  • the CO2 absorption capacity of MEA with MgO-700 NPs increased by about 31.8%.
  • the catalytic effect of MgO NPs on CO2 desorption was examined with the used MEA sorbent obtained after about 3,600 seconds of CO2 sorption.
  • FIG. 8B shows the curve of the desorption rate in FIG. 8B.
  • adding the MgO NP catalyst increases the CO 2 desorption to about 8,740% at about 200 s (FIG.8B inset).
  • the inset of FIG.9B shows the percentage increase in CO 2 desorption quantity as a result of using MgO NPs described herein.
  • the accumulated desorbed CO2 concentration of the catalyzed spent MEA with MgO NPs at about 260 s was about 2,290% greater than that of the uncatalyzed spent MEA when compared to the CO2 desorption of the uncatalyzed spent MEA.
  • the accumulation curve of CO2 desorption shows that the MgO NPs calcined at different temperatures can play a significant role.
  • the cumulative desorption amounts of MgO-700, MgO-900, and MgO-1100 are about 113.7 mmol, about 108.3 mmol, and about 105.5 mmol, respectively under the conditions tested.
  • MgO-700 has the highest desorption capacity.
  • the amount of CO2 absorbed and desorbed on MgO NPs increased in the order of MgO- 1100 ⁇ MgO-900 ⁇ MgO-700.
  • Table 4 provides a summary of absorption enhancement performance of CO 2 absorption/desorption for an example absorbent (Ex. 1). Table 4 also shows comparative examples absorbents from recent studies on the improvement of CO 2 absorption driven by nanoparticles. Maximum enhancement ratio of absorption is calculated as the ratio of the maximum amount of CO2 sorbed with the use of nanoparticles to that without the use of nanoparticles. The significantly improved CO 2 capture performance of mesoporous MgO described herein may be attributed to its surface being enhanced with oxygen vacancies and basic sites. Table 4 Maximum Size and E xample Absorbent Nanoparticles enhancement ratio concentration of Abs.
  • the cumulative absorbed CO 2 quantity of the sample with the MgO-700 NPs is higher than that without MgO-700 NPs.
  • the first-tenth cycle curves and the zeroth cycle curve almost overlap in the first 800s.
  • the kinetics of the first-tenth cycle curves drop significantly.
  • FIGS. 11F-11H after the catalyst was added, the cumulative amount in the desorption cycle was close to the sample without the catalyst. However, the desorption rate of the sample with the catalyst is significantly higher (FIGS. 11D-11E).
  • the cyclic CO 2 absorption-desorption capabilities of 20 wt % MEA solution catalyzed by about 2 wt% MgO NPs for 50 consecutive runs are shown in FIG.10B.
  • the data indicates that the MgO nanoparticles described herein have good long-cycling stability with about 97.2% absorption capacity retention after 50 cycles.
  • the results also indicate that MgO- 700 NPs may maintain, recover, and regenerate the active sites after being subjected to 50 cycles. It was also found that the MgO-700 NPs can maintain consistent efficiency after repeated use.
  • MgO is an eco-friendly and nontoxic material widely used in various industries. Developing recyclable technologies for metal resources can be a cost-effective way to avoid repeated metallurgical processes and reduce greenhouse gas emissions.
  • the MgO nanoparticles can be recycled by filtration, and then additional washing steps for recycled MgO can be performed. This wastewater from other washing steps can be reused in CO 2 absorbents.
  • Raman spectroscopy was utilized to confirm that MgO NPs had a catalytic effect on the absorption and desorption of CO 2 .
  • Raman spectra of MEA aqueous solutions with and without 2 wt% MgO-700 NPs were examined to observe the effect of the catalyst on the absorption step. The findings are shown in FIG. 12A and FIG. 13A.
  • the peaks at about 1012 cm ⁇ 1 , about 1063 cm ⁇ 1 , and about 1153 cm ⁇ 1 represent the C–OH stretch of HCO 3 ⁇ , the C–O stretch of and the C–N stretch of RNHCO 2 ⁇ , respectively.
  • RNHCO 2 ⁇ production can reach its peak height more quickly than without using the catalyst.
  • the peak intensity of HCO 3 ⁇ after the first 20 minutes of catalyzed CO 2 sorption can be higher than that achieved without the MgO-700 NPs catalyst.
  • the peak intensities of HCO 3 ⁇ and RNHCO 2 ⁇ can gradually decrease with the CO 2 desorption time.
  • the CO 3 2 ⁇ peak intensity of the catalytic spent MEA solution can decrease slower than that of the uncatalyzed one.
  • all of the HCO 3 ⁇ , CO 3 2 ⁇ , and RNHCO 2 ⁇ can have their peak heights decreased at higher rates.
  • the peak HCO 3 ⁇ intensity in the MEA solution with MgO NPs can decrease significantly. This result suggests that the MgO-700 NPs can be responsible for the substantial catalytic increase of CO 2 desorption.
  • Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO 2 absorption, CO 2 desorption, and/or CO 2 capture processes. [0154] Overall, embodiments of the present disclosure provide a facile, efficient, and scalable co-precipitation-calcination process using PEG (e.g., PEG 1500) as an example soft template to synthesize mesoporous MgO NPs at various temperatures (about 500°C, about 700°C, about 900°C, and about 1100°C).
  • PEG e.g., PEG 1500
  • the MgO surface structure can be nonstoichiometric due to its distinctive shape, which includes several surface hydroxyl groups and lattice defects from its calcination process. Strong catalytic activity can be provided by oxygen vacancies, which is supported by basic sites from the TPD-CO 2 investigations that have varying strengths and relative concentrations.
  • MgO NPs can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by about 3,000% or more and can increase the CO2 absorption capacity within the breakthrough time by about 3,660% or more, and increased the maximum CO 2 desorption rate by about 8,740% or more at about 200 s.
  • Clause A1 or Clause A2 wherein the MgO is in the form of particles, the particles having: an average particle size that is from 8 nm to about 70 nm; an average pore diameter that is from about 2 nm to about 20 nm; a specific surface area that is about 500 m 2 g –1 or less, such as about 250 m 2 g –1 or less; a total pore volume that is about 1 cm 3 g –1 or less; or combinations thereof.
  • Clause A4 The composition of any one of Clauses A1-A3, further comprising water.
  • Clause A4 The composition of any one of Clauses A1-A4, wherein an amount of the MgO in the composition is about 5 wt% (50,000 ppm) or less based on a total weight of the composition.
  • Clause A6 The composition of any one of Clauses A1-A5, wherein an amount of the MgO in the composition is about 2.5 wt% (25,000 ppm) or less based on a total weight of the composition.
  • Clause A7 The composition of any one of Clauses A1-A6, wherein the organic amine comprises a primary amine compound, a secondary amine compound, a tertiary amine compound, or combinations thereof.
  • composition of any one of Clauses A1-A7, wherein the organic amine comprises monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), or combinations thereof.
  • the organic amine comprises monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), or combinations thereof.
  • DETA diethylenetriamine
  • TETA triethylenetetramine
  • TEPA tetraethylenepentamine
  • TAED tetraacetylethylenediamine
  • PEHA pentaethylenehexamine
  • PEI polyethyleneimine
  • Clause B2. The process of Clause B1, wherein the additive comprises a surfactant, an antifoaming agent, or combinations thereof.
  • a process for capturing carbon dioxide (CO 2 ) from a gas stream comprising: introducing a gas stream with a composition under absorption conditions, the gas stream comprising CO2, the composition comprising: an organic amine, an ion, thereof, or combinations thereof; magnesium oxide (MgO); and optionally water, an ion thereof, or a combination thereof; and forming a CO 2 -enriched composition.
  • Clause C2 The process of Clause C1, wherein the composition comprises the composition of any one of Clauses A1-A10 and/or the composition made according to any one of Clauses B1-B2.
  • Clause C3 The process of Clause C1 or Clause C2, wherein at least a portion of the composition is ultrasonically pretreated.
  • Clause D1 A process for desorption of carbon dioxide (CO 2 ) from a CO 2 - enriched composition, the process comprising: heating a CO 2 -enriched composition under desorption conditions, the CO 2 - enriched composition comprising: an organic amine, an ion thereof, or a combination thereof; magnesium oxide (MgO); and optionally water, an ion thereof, or a combination thereof; and separating CO2 from the CO2-enriched composition to form a CO2-depleted composition.
  • CO 2 carbon dioxide
  • a process for capturing carbon dioxide (CO 2 ) from a gas stream comprising: contacting the gas stream with a composition, under absorption conditions, in an absorption unit to form a CO 2 -enriched composition, the gas stream comprising CO 2 , the composition comprising the composition of any one of Clauses A1-A10 and/or the composition made according to any one of Clauses B1-B2; passing the CO 2 -enriched composition to a desorption unit; heating at least a portion of the CO2-enriched composition in the desorption unit; separating CO2 from the CO2-enriched composition to form a CO2-depleted composition; and regenerating the composition from at least a portion of the CO 2 -depleted composition, recycling at least a portion of the CO 2 -depleted composition to the absorption unit, or both.
  • CO 2 carbon dioxide
  • Clause F1 A process for forming magnesium oxide particles, comprising: forming a mixture comprising a magnesium source, a templating agent, a base, and a solvent; and drying and/or calcining the mixture at a temperature of about 450°C to about 1200°C to form magnesium oxide particles.
  • Clause F2. The process of Clause F1, wherein: the templating agent comprises a polyethylene glycol; the base comprises an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof; or combinations thereof.
  • a process for forming mesoporous magnesium oxide particles comprising: forming a mixture comprising a magnesium source and a templating agent in a liquid; introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles; separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles; and calcining the as-synthesized form of the mesoporous magnesium oxide particles under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles.
  • Clause G1 wherein the introducing the base to the mixture to precipitate the as-synthesized form of the mesoporous magnesium oxide particles comprises sonicating the mixture while introducing the base to the mixture.
  • Clause G3 The process of Clause G1 or Clause G2, wherein the calcination conditions comprise a calcination temperature that is from about 450°C to about 1200°C.
  • Clause G4 The process of any one of Clauses G1-G3, wherein: the base comprises an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof; and/or the liquid is water.
  • Clause G1-G4 wherein, when the base comprises the alkali metal carbonate, the alkali metal carbonate comprises lithium, sodium, or potassium.
  • Clause G6 The process of any one of Clauses G1-G5, wherein the base comprises sodium carbonate (Na2CO3).
  • Clause G7 The process of any one of Clauses G1-G6, wherein the templating agent comprises a glycol.
  • Clause G8 The process of any one of Clauses G1-G7, wherein the templating agent comprises a polyethylene glycol. [0184] Clause G9.
  • a process for forming mesoporous magnesium oxide particles comprising: forming a mixture comprising a magnesium source and a templating agent in a liquid; introducing an aqueous base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles, the aqueous base comprising an alkali metal carbonate; separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles; and calcining the as-synthesized form of the mesoporous magnesium oxide particles at a temperature that is from about 450°C to about 1200°C to form a calcined form of the mesoporous magnesium oxide particles, the calcined form of the mesoporous magnesium oxide particles having a specific surface area that is from about 100 m 2 g –1 to about 800 m 2 g –1 .
  • Clause H2 The process of Clause H1, wherein the specific surface area of the calcined form of the mesoporous magnesium oxide particles is from about 100 m 2 g –1 to about 400 m 2 g –1 .
  • Clause I1 A process for capturing carbon dioxide (CO 2 ), the process comprising: introducing or contacting a composition with a gas stream comprising CO 2 , the composition comprising the mesoporous magnesium oxide particles made according to any one of Clauses G1-G12 or H1-H2.
  • a process for capturing carbon dioxide (CO2) from a gas stream comprising: introducing a gas stream comprising CO 2 with a composition under absorption conditions, the composition comprising: an organic amine; calcined mesoporous magnesium oxide particles having a specific surface area that is from about 100 m 2 g –1 to about 800 m 2 g –1 ; and optionally water; and forming a CO2-enriched composition.
  • Clause J2 The process of Clause J1, wherein at least a portion of the composition is ultrasonically pretreated prior to introducing the gas stream to the composition.
  • the organic amine in the composition comprises monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA), polyethyleneimine (PEI), or combinations thereof.
  • MEA monoethanolamine
  • DEA diethanolamine
  • TAA diisopropanolamine
  • DEMEA diethyl-monoethanolamine
  • DETA diethylenetriamine
  • TETA triethylenetetramine
  • TEPA tetraethylenepentamine
  • TAED tetraacetylethylenediamine
  • polyethylenehexamine such as pentaethylenehexamine
  • Clause J6 The process of any one of Clauses J1-J5, wherein the calcined mesoporous magnesium oxide particles have: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; or combinations thereof.
  • All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures to the extent they are not inconsistent with this text.
  • compositions, an element, a group of elements, or a method are preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same composition, method, or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “Is” preceding the recitation of the composition, element, elements, or method, and vice versa, such as the terms “comprising,” “consisting essentially of,” “consisting of” also include the product of the combinations of elements listed after the term.
  • ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited.
  • the recitation of the numerical range 1 to 5 includes the subranges 1 to 4, 1.5 to 4.5, 1 to 2, among other subranges.
  • the recitation of the numerical ranges 1 to 5, such as 2 to 4 includes the subranges 1 to 4 and 2 to 5, among other subranges.
  • within a range includes every point or individual value between its end points even though not explicitly recited.
  • the recitation of the numerical range 1 to 5 includes the numbers 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, among other numbers.
  • every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.
  • the indefinite article “a” or “an” shall mean “at least one” unless specified to the contrary or the context clearly indicates otherwise.
  • embodiments comprising “an organic amine” include embodiments comprising one, two, or more organic amines, unless specified to the contrary or the context clearly indicates only one organic amine is included.

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Abstract

Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO2 absorption, CO2 desorption, and/or CO2 capture processes. In an embodiment, a process for forming mesoporous magnesium oxide particles is provided. The process includes forming a mixture comprising a magnesium source and a templating agent in a liquid. The process further includes introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles. The process further includes separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles. The process further includes calcining the as-synthesized form of the mesoporous magnesium oxide particles under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles.

Description

Attorney Docket No.: UWYO/0090PC PREPARATION OF MAGNESIUM OXIDE AND CARBON DIOXIDE CAPTURE USING MAGNESIUM OXIDE GOVERNMENT RIGHTS [0001] The invention was made with government support under Grant No. 1632899 awarded by the National Science Foundation. The government has certain rights in the invention. FIELD [0002] Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO2 absorption, CO2 desorption, and/or CO2 capture processes. BACKGROUND [0003] Carbon dioxide (CO2) is a primary greenhouse gas that contributes greatly to global warming, owing to the excessive emissions from the combustion of fossil fuels. Carbon capture, utilization, and storage (CCUS) is the mature technology that can be carried out to alleviate the CO2 discharge, which is urgently needed for achieving the goals set in the Paris Climate Accord. Amine-based CO2 absorption is a potentially cost- effective option for capturing CO2 from gas streams (e.g., flue gas) and the atmosphere. CO2 capture is critical because of its increasing importance as a resource for material and fuel synthesis. [0004] A fundamental challenge of chemisorption-based technologies is the slow absorption and desorption reaction kinetics when CO2 desorption reaches temperatures greater than 100°C. Here, excessive energies may be needed to vaporize a large amount of liquid water during the CO2 desorption operation and condense the same amount of water vapor prior to CO2 desorption during cyclic CO2 sorption and desorption. Monoethanolamine (MEA) solution has a low price and high reactivity with CO2, which applies to the benchmark solvent for evaluating amine-based CO2 capture processes at a small scale. However, this technology is still not acceptable for versatile and large-scale uses mainly attributed to (1) the critical limitations for >100°C CO2 desorption or energy- intensive MEA regeneration process, and (2) the resultant aggregated MEA degradation, as well as (3) severe corrosion at such high temperatures. In other words, to render fast CO2 desorption from aqueous solvent, high temperature (120-140 °C) conditions are utilized with state-of-the-art methods, resulting in excessive energy demands for the water vaporization. [0005] There is a need for new and improved magnesium oxide particles and processes for making. New and improved compositions are also needed for the absorption, desorption, and/or capture of CO2. SUMMARY [0006] Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO2 absorption, CO2 desorption, and/or CO2 capture processes. Unlike conventional methods, embodiments of the present disclosure enable synthesis of mesoporous magnesium oxide (MgO) nanoparticles in an efficient and scalable manner via precipitation and calcination at various temperatures. The surface structure of the MgO can be nonstoichiometric due to its distinctive shape, which may include several surface hydroxyl groups and lattice defects from its calcination process. Strong catalytic activity can be provided by oxygen vacancies. The MgO nanoparticles show significantly improved breakthrough times, increased absorption capacity, and increased maximum CO2 desorption rate. Further, the MgO NPs can maintain steady efficiency for CO2 absorption and desorption even after repeated usage with no discernible decline in the catalytic impact of MgO. [0007] In an embodiment, a process for forming mesoporous magnesium oxide particles is provided. The process includes forming a mixture comprising a magnesium source and a templating agent in a liquid. The process further includes introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles. The process further includes separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles. The process further includes calcining the as-synthesized form of the mesoporous magnesium oxide particles under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles. [0008] In another embodiment, a process for forming mesoporous magnesium oxide particles is provided. The process includes forming a mixture comprising a magnesium source and a templating agent in a liquid. The process further includes introducing an aqueous base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles, the aqueous base comprising an alkali metal carbonate. The process further includes separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles. The process further includes calcining the as- synthesized form of the mesoporous magnesium oxide particles at a temperature that is from about 450°C to about 1200°C to form a calcined form of the mesoporous magnesium oxide particles, the calcined form of the mesoporous magnesium oxide particles having a specific surface area that is from about 100 m2g–1 to about 800 m2g–1. [0009] In another embodiment, a process for capturing carbon dioxide (CO2) is provided. The process includes introducing or contacting a composition with a gas stream comprising CO2, the composition comprising mesoporous magnesium oxide particles described herein. [0010] In another embodiment, a process for capturing carbon dioxide (CO2) from a gas stream is provided. The process includes introducing a gas stream comprising CO2 with a composition under absorption conditions, the composition comprising: an organic amine; calcined mesoporous magnesium oxide particles having a specific surface area that is from about 100 m2g–1 to about 800 m2g–1; and optionally water. The process further includes forming a CO2-enriched composition. [0011] In an embodiment, a composition for absorbing or desorbing carbon dioxide (CO2) is provided. The composition includes an organic amine, and magnesium oxide. [0012] In another embodiment, a process for making a composition for absorbing or desorbing carbon dioxide (CO2) is provided. The process includes ultrasonically treating a mixture comprising MgO particles, organic amine, and water; and optionally introducing an additive to the mixture to form a composition for absorbing or desorbing carbon dioxide. [0013] In another embodiment, a process for capturing carbon dioxide (CO2) from a gas stream is provided. The process includes introducing a gas stream with a composition described herein under absorption conditions, the gas stream comprising CO2. The process further includes forming a CO2-enriched composition. In some embodiments, at least a portion of the composition is ultrasonically pretreated. [0014] In another embodiment, a process for desorption of carbon dioxide (CO2) from a CO2-enriched composition. The process includes heating a CO2-enriched composition under desorption conditions, the CO2-enriched composition comprising: an organic amine, an ion thereof, or a combination thereof; magnesium oxide (MgO); and optionally water, an ion thereof, or a combination thereof. The process further includes separating CO2 from the CO2-enriched composition to form a CO2-depleted composition. [0015] In another embodiment, a process for capturing carbon dioxide (CO2) from a gas stream is provided. The process includes contacting the gas stream with a composition described herein, under absorption conditions, in an absorption unit to form a CO2-enriched composition, the gas stream comprising CO2. The process further includes passing the CO2-enriched composition to a desorption unit, and heating at least a portion of the CO2- enriched composition in the desorption unit. The process further includes separating CO2 from the CO2-enriched composition to form a CO2-depleted composition. The process further includes regenerating the composition from at least a portion of the CO2-depleted composition, recycling at least a portion of the CO2-depleted composition to the absorption unit, or both. [0016] In another embodiment, a process for forming magnesium oxide particles is provided. The process includes forming a mixture comprising a magnesium source, a templating agent, a base, and a solvent. The process further includes drying and/or calcining the mixture at a temperature of about 450°C to about 1200°C to form magnesium oxide particles. BRIEF DESCRIPTION OF THE DRAWINGS [0017] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments. [0018] FIG. 1 is a schematic diagram of an example experimental setup for carbon dioxide (CO2) absorption and desorption experiments according to at least one embodiment of the present disclosure. [0019] FIG. 2 shows exemplary X-ray diffraction (XRD) patterns of example MgO products calcined at temperatures ranging from about 500°C to about 1,100°C according to at least one embodiment of the present disclosure. [0020] FIG. 3A is an exemplary transmission electron microscopy (TEM) image of example products calcined at about 500°C (MgO-500 particles) according to at least one embodiment of the present disclosure. [0021] FIG. 3B is an exemplary scanning transmission electron microscopy (STEM) image of example MgO-500 particles according to at least one embodiment of the present disclosure. [0022] FIGS. 3C-3F are exemplary X-ray energy-dispersive spectroscopy (XEDS) images of example MgO-500 particles according to at least one embodiment of the present disclosure. [0023] FIG. 3G is an exemplary TEM image of example products calcined at about 700°C (MgO-700 particles) according to at least one embodiment of the present disclosure. [0024] FIG. 3H is an exemplary STEM image of example MgO-700 particles according to at least one embodiment of the present disclosure. [0025] FIGS. 3I-3L are exemplary XEDS images of example MgO-700 particles according to at least one embodiment of the present disclosure. [0026] FIG. 3M is an exemplary TEM image of example products calcined at about 900°C (MgO-900 particles) according to at least one embodiment of the present disclosure. [0027] FIG. 3N is an exemplary STEM image of example MgO-900 particles according to at least one embodiment of the present disclosure. [0028] FIGS. 3O-3R are exemplary XEDS images of example MgO-900 particles according to at least one embodiment of the present disclosure. [0029] FIG. 3S is an exemplary TEM image of example products calcined at about 1,100°C (MgO-1100 particles) according to at least one embodiment of the present disclosure. [0030] FIG. 3T is an exemplary STEM image of example MgO-1100 particles according to at least one embodiment of the present disclosure. [0031] FIGS. 3U-3X are exemplary XEDS images of example MgO-1100 particles according to at least one embodiment of the present disclosure. [0032] FIG. 4A shows exemplary data for nitrogen (N2) absorption-desorption isotherms for example MgO-700 particles, MgO-900 particles, and MgO-1100 particles according to at least one embodiment of the present disclosure. [0033] FIG.4B shows exemplary data for the pore size distributions of example MgO- 700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure. [0034] FIG. 5A shows exemplary survey X-ray photoelectron spectroscopy (XPS) spectra of example MgO-700 particles, example MgO-900 particles, and example MgO- 1100 particles according to at least one embodiment of the present disclosure. [0035] FIG. 5B shows exemplary high-resolution XPS spectra of the Mg 2p peak of example MgO-700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure. [0036] FIG.5C shows exemplary high-resolution XPS spectra of the Mg O 1s peak of example MgO-700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure. [0037] FIG.6 shows exemplary data for the temperature programmed desorption CO2 (TPD-CO2) profiles for example MgO-700 particles, example MgO-900 particles, and example MgO-1100 particles according to at least one embodiment of the present disclosure. Also shown are pictorial representations of example CO2 absorbed species over weak basic sites, medium basic sites, and strong basic sites according to at least one embodiment of the present disclosure. [0038] FIG.7A is a pictorial representation of major reaction pathways of CO2 capture of a 20 wt% MEA solution without MgO particles according to at least one embodiment of the present disclosure. [0039] FIG.7B is a pictorial representation of major reaction pathways of CO2 capture of a 20 wt% MEA solution with example MgO particles according to at least one embodiment of the present disclosure. [0040] FIG. 8A is exemplary data showing the effects of example catalysts (MgO particles) on the CO2 absorption quantity and (Cin-Cout)/Cin of a 20 wt% monoethanolamine (MEA) solution catalyzed by 2% MgO-700 particles, MgO-900 particles, or MgO-1100 particles according to at least one embodiment of the present disclosure. [0041] FIG. 8B is exemplary data showing the effects of example catalysts (MgO particles) on the CO2 desorption rate of a 20 wt% MEA solution catalyzed by 2% MgO- 700 particles, MgO-900 particles, or MgO-1100 particles according to at least one embodiment of the present disclosure. [0042] FIG. 8C is exemplary data showing the effects of example catalysts (MgO particles) on the CO2 absorption and desorption capacity of a 20 wt% MEA solution catalyzed by 2% MgO-700 particles, MgO-900 particles, or MgO-1100 particles according to at least one embodiment of the present disclosure. (Error bars represent standard deviations from three independent experiments.) [0043] FIG. 9A is exemplary data showing the effects of example catalysts (MgO particles) on CO2 absorption amount of a 20 wt% MEA solution catalyzed by 2wt % MgO- 700, MgO-900, or MgO-1100 NPs according to at least one embodiment of the present disclosure. [0044] FIG. 9B is exemplary data showing the effects of example catalysts (MgO particles) on CO2 desorption amount of a 20 wt% MEA solution catalyzed by 2wt % MgO- 700, MgO-900, or MgO-1100 NPs according to at least one embodiment of the present disclosure. [0045] FIG. 10A shows exemplary data for the cyclic performance of a 20
Figure imgf000010_0001
MEA solution without and with example MgO-700 particles on CO2 absorption and desorption according to at least one embodiment of the present disclosure. [0046] FIG. 10B is exemplary data showing the stability of MEA/MgO-700 particles CO2 capture system according to at least one embodiment of the present disclosure. [0047] FIGS. 11A, 11B, and 11C show exemplary data for the cyclic performance of example MgO particles demonstrating the effects of the catalysts (MgO particles) on CO2 absorption amount according to at least one embodiment of the present disclosure. [0048] FIGS.11D and 11E show exemplary data for the cyclic performance of example MgO particles demonstrating the effects of the catalysts (MgO particles) on CO2 desorption rate according to at least one embodiment of the present disclosure. [0049] FIGS. 11F, 11G, and 11H show exemplary data for the cyclic performance of example MgO particles demonstrating the effects of the catalysts (MgO particles) on CO2 desorption amount according to at least one embodiment of the present disclosure. [0050] FIG. 12A shows exemplary Raman spectra of the CO2 absorption of MEA aqueous solutions without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure. (The indicated times were the periods when samples were taken during absorption for Raman spectral analysis. The peak intensities are proportional to the concentration of species in solution.) [0051] FIG. 12B shows exemplary Raman spectra of the CO2 desorption of MEA aqueous solutions without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure. (The indicated times were the periods when samples were taken during desorption tests for Raman spectral analysis. The peak intensities are proportional to the concentration of species in solution.) [0052] FIG. 13A shows three-dimensional (3D) surface plots of the Raman intensity of CO2 absorption without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure. [0053] FIG. 13B shows 3D surface plots of the Raman intensity of CO2 desorption without MgO particles and with example MgO particles at different times according to at least one embodiment of the present disclosure. [0054] FIG. 14 is a non-limiting graphical representation of selected embodiments of the present disclosure. [0055] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. DETAILED DESCRIPTION [0056] Embodiments of the present disclosure generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO2 absorption, CO2 desorption, and/or CO2 capture processes. [0057] Briefly, and in some embodiments, the compositions can be aqueous compositions that include an organic amine and magnesium oxide (MgO). The MgO can be in the form particles such as nanoparticles (NPs), though microparticles and macroparticles (among other sizes of particles) are contemplated. In some embodiments, the MgO can be mesoporous, having a pore size of about 2 nanometers (nm) to about 50 nm, though other pore sizes such as microporous (pore size of up to about 2 nm) and macroporous (pore size greater than about 50 nm) are contemplated. The MgO surface structure can be nonstoichiometric due to its distinctive shape, and the abundant Lewis base sites provided by oxygen vacancies can promote CO2 capture. [0058] In some embodiments, the mesoporous MgO nanoparticles (MgO-NPs) can be made using polyethylene glycol (PEG) (e.g., PEG 1500) as a soft template. The mesoporous MgO-NPs can accelerate and/or catalyze both sorption and desorption from the organic amine (e.g., monoethanolamine (MEA)) in a superior manner relative to conventional technologies, where industrial applications of conventional CO2 capture technologies are limited by their slow CO2 sorption and desorption kinetics. [0059] In some non-limiting examples, adding about 2 wt % MgO-NPs to about 20 wt % MEA can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by about 3,000% and can increase the CO2 absorption capacity within the breakthrough time by about 3,660 %. The data suggest that, under the conditions tested, MgO-NPs can accelerate the rate and increase CO2 desorption capacity by up to about 8,740% and about 2,290% at about 90°C, respectively. In addition, the excellent stability of the system within 50 cycles is verified. These non-limiting findings demonstrate a new strategy to innovate MEA absorbents that can be used in, e.g., commercial post-combustion CO2 capture plants. [0060] The consequences of global warming have drawn significant attention as global warming directly leads to natural disasters, such as melting polar and plateau glaciers, thawing the permafrost, shrinking food production areas, mass extinction of biological species, and a lack of freshwater resources. Fossil fuel-based power generation remains the most reliable method for generating electricity, making up more than 80% of the global energy supply. However, fossil fuel combustion generates more than 25% of CO2 emissions, which is linked to global climate change. Thus, rapidly deployable flue gas treatment methods that reduce CO2 emission while allowing traditional plants to continue operating are vital to minimizing global climate change while sustaining current energy demands. [0061] At coal-fired power plants, CO2 makes up a significant portion of the 1 atm pressure fuel gas: 10-15%. As a result, using post-combustion capture processes will make it possible to convert the gas mixture with relatively high CO2 concentration into pure gas. The most common post-combustion CO2 capture methods used in many industrial plants are chemical absorption processes with monoethanolamine (MEA)-based solvents. MEA solvents have been used for over a decade to remove acidic gases from natural gas streams, such as carbon dioxide and hydrogen sulfide. Solvents containing MEA have many advanced properties that make them suitable for capturing CO2, such as low molecular weight, low solubility for hydrocarbons, high resistance to thermal degradation, a high absorption rate, and low solvent cost. However, MEA has significant drawbacks that cannot be overlooked. Such drawbacks include a low CO2 absorption ability, amine oxidation-related deterioration, high vapor pressure-related vaporization losses, and high viscosity. Therefore, degradation and corrosion considerations can be prevented by using a relatively low mass fraction, around 20 to 30% amine to H2O. As a result, the equipment needs to be relatively large, and solvent regeneration is expensive. MEA-based post- combustion CO2 capture technology does not require significant changes to the existing facilities of the power plants. Thus, it has a broad market prospect. [0062] Research has recently been conducted on designing new techniques or pathways for CO2 capture using alkanolamine-based solvents. One particular example is sorption enhanced by nanoparticles (NPs) catalysts. Both the mass transfer and reaction kinetics can be improved by adding NPs catalysts. NPs can reduce the mass transfer resistance and increase the reaction rate, reducing the equipment size, capital investment, and operating cost. Porous materials with pore sizes in the nanoscale range can offer a high absorption volume and good selectivity in the CO2 absorption process. Thus adding the porous catalyst in CO2 capture systems can enhance CO2 absorption. [0063] Many researchers have investigated the use of different materials to assist CO2 capture. These materials include metal oxides, metal-organic frameworks (MOF), zeolites, porous polymers, and porous carbons. Nevertheless, finding appropriate materials with desirable characteristics, such as sizeable particular surface area and efficient porosities, and at an affordable cost, remains elusive. [0064] The particle size, specific surface area, and bonding ability of nanoparticles with CO2 can all be factors that can affect the catalytic activities of metal oxide catalysts. [0065] For purposes of the present disclosure, the term “magnesium oxide particles” is used interchangeably with the term “catalyst” such that reference to one includes reference to the other. For example, reference to magnesium oxide particles includes reference to both magnesium oxide particles and catalyst, and vice-versa, unless the context indicates otherwise. The magnesium oxide particles can serve to catalyze the absorption of CO2 to the organic amine and/or catalyze the desorption of CO2 from the organic amine. During sorption and/or desorption, one or more components of the composition can exist as ion(s). [0066] The use of headings is for purposes of convenience only and does not limit the scope of the present disclosure. Embodiments described herein can be combined with other embodiments. [0067] As used herein, a “composition” can include component(s) of the composition, reaction product(s) of two or more components of the composition, a remainder balance of remaining starting component(s), or combinations thereof. Compositions of the present disclosure can be prepared by any suitable mixing process. [0068] As used herein, “composition enriched in CO2”, “carbon dioxide-enriched composition” and “CO2-enriched composition” means that the relative amount (or concentration) of CO2 in a composition after exposure or contact with CO2 is greater than the relative amount of CO2 in a composition before the exposure or contact. For example, if a composition includes 1% CO2 before exposure or contact with CO2, the composition after exposure or contact with CO2 would include greater than 1% CO2. The CO2 that is sequestered by one or more components of the composition can be in the form of carbonate (CO3 2í), bicarbonate (HCO3 í), a salt thereof, a reaction product with one or more components of the composition (e.g., a urethane, carbamate, or ion thereof), a physically bound CO2 by electrostatic interactions, for example, Van der Waals forces, or combinations thereof [0069] As used herein, “carbon dioxide-depleted composition” and “CO2-depleted composition” means that the relative amount (or concentration) of CO2 in a composition after desorption or release of CO2 is less than the relative amount of CO2 in a composition before the desorption or release. For example, if a composition includes 1% CO2 before desorption or release of CO2, the composition after desorption or release would include less than 1% CO2. Example Process for Forming MgO particles [0070] Embodiments of the present disclosure also relate to processes for forming MgO particles, such as those MgO particles described herein. The MgO particles can be nanoparticles. The MgO particles can be mesoporous. The MgO particles can be prepared by a precipitation method using an organic templating agent. [0071] In some embodiments, a process for forming MgO particles generally includes forming a mixture comprising a magnesium source, a templating agent, a base, and a solvent; and drying and/or calcining the mixture at a temperature of about 450°C to about 1200°C to form magnesium oxide particles. Examples of magnesium sources, templating agents, bases, and solvents are described below. [0072] A process for forming mesoporous magnesium oxide particles can include forming a mixture comprising a magnesium source and a templating agent in a liquid or liquid medium. The liquid or liquid medium can include any suitable liquid such as water. [0073] The magnesium source can be any suitable magnesium source, such as a source comprising magnesium and a ligand and/or a counterion. Counterions and ligands include one or more of halide (for example, I–, Br–, Cl–, or F–), acetylacetonate (O2C5H7–), hydride (H–), SCN–, NO2–, NO3–, N3–, OH–, oxalate (C2O42–), H2O, acetate (CH3COO–), O2–, CN–, OCN–, CNO–,NH2–, NC–, NCS–, N(CN)2–, pyridine (py), ethylenediamine (en), 2,2’- bipyridine (bipy), PPh3, or combinations thereof. Hydrates are also contemplated. An illustrative, but non-limiting, example of a magnesium source includes magnesium nitrate hexahydrate (Mg(NO3)2 ā 6H2O). [0074] The templating agent can be any suitable templating agent, such as a glycol. Illustrative, but non-limiting examples of glycols can include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (PEG), polypropylene glycol (PPG), or combinations thereof, among others. The PEG and/or PPG can have any suitable molecular weight such as from about 200 g/mol to about 100,000 g/mol, such as from about 400 g/mol to about 50,000 g/mol, such as from about 500 g/mol to about 3,000 g/mol, such as from about 1,000 g/mol to about 2,000 g/mol, such as from about 1,300 g/mol to about 1,700 g/mol, such as about 1,500 g/mol, though other values are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. In at least one example, the templating agent comprises PEG 1500. [0075] A weight ratio of the magnesium source to the templating agent in the mixture can be from about agent is from about 10:1 to about 1:1, such as from about 8:1 to about 2:1, such as from about 6:1 to about 4:1, such as about 5:1, though other values are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. [0076] The process further includes introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles. The base can be any suitable base such as a metal carbonate, such as an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof. Suitable alkali metal carbonates include carbonates of lithium, sodium, potassium, rubidium, cesium, francium, or combinations thereof. Suitable alkaline earth metal carbonates include carbonates of beryllium, magnesium, calcium, strontium, barium, radium, or combinations thereof. A non-limiting example of a base includes sodium carbonate (Na2CO3), lithium carbonate (Li2CO3), potassium carbonate (K2CO3), or combinations thereof, such as sodium carbonate. The base can be in the form of an aqueous solution. [0077] After introducing the base, the resulting mixture is maintained under sufficient conditions to precipitate the as-synthesized form of the mesoporous magnesium oxide particles and optionally occluded templating agent. These conditions can include a sufficient time for adequate precipitation, for example, from 2 hours to 168 hours. The temperature of the reaction mixture may be maintained or adjusted to a sufficient precipitation temperature, for example, from room temperature (e.g., 20°C) to about 150°C. [0078] In some embodiments, introducing the base to the mixture to precipitate the as- synthesized form of the mesoporous magnesium oxide particles includes vigorously stirring the mixture while introducing the base to the mixture. Stirring while introducing the base can be performed at suitable rotation speeds, such as from about 50 revolutions per minute (rpm) to about 1,500 rpm, such as from about 100 rpm to about 1,000 rpm, such as from about 200 rpm to about 800 rpm, such as from about 300 rpm to about 700 rpm, such as from about 400 rpm to about 600 rpm, such as from about 450 rpm to about 550 rpm, such as about 500 rpm. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other rotation speeds are contemplated and can be selected based on the ability to mix the components sufficiently. Additionally or alternatively, the mixture can be sonicated or ultrasonicated while introducing the base to the mixture. Vigorous stirring, sonication, or ultrasonication of the mixture can make the surface of the forming metal oxides (e.g., MgO) more uniform and have a larger surface area. The base can be added slowly, such as over a period of about 30 seconds to about 30 minutes, such as from about 1 minute to about 10 minutes, though other periods are contemplated. [0079] The precipitate can be separated from liquid remaining in the mixture by an appropriate technique or techniques, for example, by decantation, washing, e.g., with deionized water and/or an alcohol (e.g., ethanol), filtration, drying, or combinations thereof. Drying may take place under sufficient drying conditions, such as in air or an inert atmosphere, e.g., in nitrogen, at a sufficient temperature, for example, from 50°C to about 150°C, such as from about 80°C to about 120° C., for a sufficient time, for example, from 2 hours to 50 hours, such as from about 5 hours to about 20 hours, such as from about 10 hours to about 15 hours, such as about 12 hours, though other periods are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. [0080] The precipitate containing the as-synthesized form of the mesoporous magnesium oxide particles is calcined under conditions under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles. The calcination conditions can be sufficient to remove residual templating agent, to remove residual water, or combinations thereof. The calcination conditions can include heating the as-synthesized form of the mesoporous magnesium oxide particles at a suitable temperature that is from about 450°C to about 1200°C, such as from about 500°C to about 1100°C, such as from about 600°C to about 1000°C, such as from about 700°C to about 900°C, such as from about 600°C to about 800°C. Calcining can be performed at a temperature (°C) of 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, or 1200, or ranges thereof, though other temperatures are contemplated. Each of the foregoing numbers can be preceded by the word “about,” “at least about,” “less than about,” or “more than about” and any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. The calcination conditions can include heating the as-synthesized form of the mesoporous magnesium oxide particles for a suitable time, for example, from about 30 minutes to about 12 hours, such as from about 1 hour to about 5 hours, such as from about 1.5 hours to about 2.5 hours, such as about 2 hours, though other periods are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. The calcination conditions can include heating at a suitable temperature for a suitable time period in a suitable atmosphere such as, for example, air. [0081] In some embodiments, the MgO particles (such as the calcined form of the mesoporous magnesium oxide particles) can have one or more of the following properties: [0082] (a) An average pore diameter (Dp) that is from about 2 nm to about 50 nm, such as from about 2 nm to about 20 nm, such as from about 5 nm to about 15 nm, such as from about 6 nm to about 10 nm, though other average pore diameters are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. The average pore diameter is determined by the Barrett, Joyner, and Halenda (BJH) method as described in the Examples Section. [0083] (b) A specific surface area (SBET) that is from about 100 m2g–1 to about 800 m2g–1, such as about 500 m2g–1 or less, such as about 250 m2g–1 or less, or about 300 m2g– 1 or more, such as from about 300 m2g–1 to about 800 m2g–1; or from about 100 m2g–1 to about 400 m2g–1, such as from about 150 m2g–1 to about 250 m2g–1, though other specific surface areas are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. The specific surface area is determined by the Brunauer-Emmett-Teller (BET) method as described in the Examples Section. [0084] (c) A total pore volume (Vt) that is about 2 cm3g–1 or less, such as about 1 cm3g– 1 or less, such as from about 0.1 cm3g–1 to about 1 cm3g–1, such as from about 0.15 cm3g–1 to about 0.4 cm3g–1, though other total pore volumes are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. The total pore volume is determined as described in the Examples section. [0085] (d) An average particle size that is from about 5 nm to about 100 nm, such as from about 8 nm to about 70 nm, such as from about 8 nm to about 10 nm, or from about 15 nm to about 25 nm, or from about 50 nm to about 70 nm, though other values are contemplated. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. [0086] As further described below, the MgO particles described herein may be used for CO2 capture. Other non-limiting applications can include wastewater treatment and sensors. [0087] Relative to conventional methods, processes for forming MgO particles described herein can provide high surface area magnesium oxide MgO nanoparticles in a cost-effective manner. In addition, the MgO particles formed by processes described herein can be easily recycled after use in, e.g., CO2 capture or other applications. Example Composition [0088] Embodiments of the present disclosure generally relate to compositions for absorbing and/or desorbing carbon dioxide (CO2). The compositions (also referred to as catalyst compositions) generally include a solution or suspension that includes an organic amine and MgO particles. Any suitable solvent such as water may be used for dispersing, solubilizing, and/or suspending at least a portion of the MgO particles and/or the organic amine. [0089] The MgO particles serve to, e.g., catalyze and/or accelerate absorption, desorption, and/or capture of CO2. Properties of the MgO particles are described above. More than one type of MgO particle can be utilized in compositions described herein if desired. [0090] The organic amine serves to, e.g., capture and/or absorb CO2. More than one organic amine can be utilized with the compositions described herein. The organic amine(s) can include one or more primary, secondary, and/or tertiary organic amine compounds. The one or more primary, secondary, and/or tertiary organic amine compounds can include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), or combinations thereof. In some embodiments, the one or more organic amines can include amine-functionalized polymers such as polyethylene amine. The polyethylene amine can include diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA), polyethyleneimine (PEI), or combinations thereof. [0091] In some examples, an amount of MgO particles in compositions described herein can be about 0.1 wt% to about 10 wt%, such as from about 0.5 wt% to about 5 wt%, such as from about 1 wt% to about 3 wt%, such as about 2 wt% based on a total weight of the composition. In at least one embodiment, the amount (wt%) of MgO particles in compositions described herein can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, or 10, or ranges thereof. Each of the foregoing numbers can be preceded by the word “about,” “at least about,” “less than about,” or “more than about” and any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other amounts of MgO particles in the composition are contemplated. Combinations of different MgO particles can be utilized. [0092] Any of the foregoing amounts can apply to a single type of MgO particle, the total amount of a combination of MgO particles, or the total amount of all MgO particles present in the composition. The amount of MgO particles used for the compositions can be based on the dry weight of the MgO particles (e.g., the MgO particles without moisture). [0093] In some examples, an amount of organic amine in compositions described herein is about 1 wt% or more and/or about 99 wt% or less, such as from about 5 wt% to about 95 wt%, such as from about 10 wt% to about 90 wt%, such as from about 15 wt% to about 85 wt%, such as from about 20 wt% to about 80 wt%, such as from about 30 wt% to about 70 wt%, based on a total weight of the composition. In some embodiments, the amount of organic amine can be from about 5 wt% to about 40 wt%, such as from about 10 wt% to about 35 wt%, such as from about 15 wt% to about 30 wt%, such as from about 20 wt% to about 25 wt%, based on a total weight of the composition. In at least one embodiment, the amount (in wt%) of organic amine in compositions described herein can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 87, 88, 89, 91, 92, 93, 94, 95, 96, 97, 98, or 99, or ranges thereof. Each of the foregoing numbers can be preceded by the word “about,” “at least about,” “less than about,” or “more than about” and any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. For example, the amount (wt%) of organic amine in the composition is about 10 wt% or more, about 15 wt% to about 25 wt%, about 50 wt% or less, or at least about 20 wt%. Any of the foregoing amounts can apply to a single organic amine, the total amount of a combination of organic amines, or the total amount of all organic amines present in the composition. Other amounts of the one or more organic amines in the composition are contemplated. [0094] In some embodiments, compositions described herein can include any suitable additive. Illustrative, but non-limiting, examples of additives include a surfactant, an antifoaming agent, or combinations thereof, among others. The surfactant can serve to minimize agglomeration and sedimentation of MgO nanoparticles in the solution. The antifoaming agent can serve to reduce the amount of bubbles produced by the surfactant, thereby facilitating the process of packing, sampling, and testing the solution. [0095] For example, a surfactant (e.g., 1-hexadecyl trimethyl ammonium bromide (CTAB, CH3(CH2)15N(CH3)3Br) and/or an antifoaming agent (such as Antifoam 204) can be utilized in compositions described herein comprising the one or more MgO particles, the one or more organic amines, and the solvent (e.g., water). Other surfactants and antifoaming agents are contemplated. [0096] An amount of surfactant in compositions described herein can be from about 0.01 wt% to about 1 wt%, such as from about 0.1 wt% to about 1 wt%, such as from about 0.2 wt% to about 0.9 wt%, such as from about 0.3 wt% to about 0.8 wt%, such as from about 0.4 wt% to about 0.7 wt%, such as from about 0.5 wt% to about 0.6 wt%, based on the total weight of the composition. In at least one embodiment, the amount of surfactant in compositions described herein can be greater than 0 wt% and about 0.5 wt% or less, such as about 0.4 wt% or less, such as about 0.3 wt% or less, such as about 0.2 wt% or less, such as about 0.1 wt% or less, based on the total weight of the composition. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other amounts are contemplated. [0097] An amount of antifoaming agent in compositions described herein can be from about 0.01 wt% to about 1 wt%, such as from about 0.1 wt% to about 1 wt%, such as from about 0.2 wt% to about 0.9 wt%%, such as from about 0.3 wt% to about 0.8 wt%, such as from about 0.4 wt% to about 0.7 wt%, such as from about 0.5 wt% to about 0.6 wt%, based on the total weight of the composition. In at least one embodiment, the amount of antifoaming agent in compositions described herein can be greater than 0 wt% and about 0.5 wt% or less, such as about 0.4 wt% or less, such as about 0.3 wt% or less, such as about 0.2 wt% or less, such as about 0.1 wt% or less, based on the total weight of the composition. Any of the foregoing numbers can be used singly to describe an open-ended range or in combination to describe a close-ended range. Other amounts are contemplated. The amount of the surfactant and the antifoaming agent can be the same or different. Example Process for Making a Composition [0098] Embodiments of the present disclosure also relate to a process for making a composition for absorbing or desorbing carbon dioxide (CO2). The method generally includes forming a mixture of one or more MgO particles, one or more organic amines, and a solvent (e.g., water). The solvent, the one or more MgO particles, and the one or more organic amines can be mixed by suitable methods. In some examples, two or more components of the composition can be subjected to sonication or ultrasonication prior to and/or after introducing the third component to the composition. For example, a mixture of solvent and the one or more organic amines can be subjected to sonic treatment or ultrasonic treatment. The sonically- or ultrasonically-treated mixture can be introduced with the one or more MgO particles to form a composition described herein. The resulting mixture can be subjected to sonic treatment or ultrasonic treatment. [0099] In some embodiments, an additive can be added to the mixture comprising the one or more MgO particles, the one or more organic amines, and the solvent (e.g., water). Additives, such as surfactants, antifoaming agents, among others can be used, and are described above. Example Processes for Absorbing and/or Desorbing Carbon Dioxide [0100] Embodiments of the present disclosure also generally relate to processes for absorbing carbon dioxide (CO2), desorbing CO2, and/or capturing CO2. Briefly, and in some embodiments, CO2 is present in a gas or a gas stream. The gas or gas stream is introduced and/or contacted with a composition described herein, and a CO2-enriched composition is formed. The gas or gas stream can have any suitable amount of one or more gases. For example, the gas or gas stream can include CO2 with one or more other gases such as N2 and/or O2 in any suitable concentrations. [0101] In some embodiments, a process for absorbing, desorbing, and/or capturing carbon dioxide (CO2) includes contacting/introducing, under absorption conditions, a gas or gas stream with a composition described herein to form a CO2-enriched composition. The contact and/or introduction can occur in an absorption unit. The absorption conditions can include various, temperatures, pressures, times, flow rates of the gas (or gas stream) and/or other parameters suitable for absorption. [0102] After a certain period of time, at least a portion of CO2 can be desorbed (e.g., removed) from the CO2-enriched composition under desorption conditions. Such desorption can be performed in a desorption unit. The desorption unit can be the same unit as the absorption unit, except that, e.g., the unit is placed under desorption conditions. Additionally, or alternatively, the CO2-enriched composition can be passed to a separate desorption unit. Desorption conditions can include various temperatures, pressures, times, flow rates of gases into the desorption unit, and/or other parameters suitable for absorption. For example, at least a portion of the composition can be heated in the desorption unit to a temperature of about 20°C or more and/or about a temperature that is less than a boiling point of the solvent (e.g., water), for example, from about 25°C to about 100°C, such as from about 50°C to about 95°C, such as from about 70°C to about 90°C, such as about 85°C or about 90°C. Other temperatures are contemplated. CO2 is desorbed, removed, or otherwise separated from CO2-enriched composition to form a CO2-depleted composition. The CO2-depleted composition can still contain an amount of CO2. In some embodiments, after desorbing, removing, or otherwise separating CO2 from the CO2-enriched composition, a composition described herein can be regenerated from at least a portion of the CO2-depleted composition. Additionally, or alternatively, at least a portion of the CO2-depleted composition can be recycled to the absorption unit. [0104] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use aspects of the present disclosure, and are not intended to limit the scope of aspects of the present disclosure. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, dimensions, etc.) but some experimental errors and deviations should be accounted for. [0105] In some examples, mesoporous MgO NPs with abundant oxygen vacancies were prepared via the co-precipitation-calcination process with PEG 1500 as a soft template and used the resulting MgO produces as catalysts for CO2 capture. An aqueous MEA solution (20 wt%) was used as the CO2 absorbent. Investigations into how MgO NPs, with various morphologies, basic sites, and oxygen vacancies, affect the kinetic rates of CO2 capture in MEA solution were performed. Examples [0106] In some examples, mesoporous MgO NPs with abundant oxygen vacancies were prepared via the co-precipitation-calcination process with PEG 1500 as a soft template and used the resulting MgO produces as catalysts for CO2 capture. An aqueous MEA solution (20 wt%) was used as the CO2 absorbent. Therefore, investigations into how MgO NPs, with various morphologies, basic sites, and oxygen vacancies, affect the kinetic rates of CO2 capture in MEA solution were performed 1. Materials and Test Methods 1.1. Materials [0107] Unless otherwise indicated, all raw materials were analytical grade and were used as received. 1.2. Test Methods [0108] Powder X-ray diffraction (XRD) data were obtained using an X-Pert diffractometer (Philip, Holland) with Cu KĮ radiation operated at 40 kV and 40 mA. [0109] The structural features of the NPs were studied by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) (TALOS F200X, Thermo Scientific, USA) operating at an accelerating voltage of U = 200 kV, equipped with a high-angle annular dark-field detector (HAADF) (M3000, Fischione, USA), and X-ray energy-dispersive spectroscopy (XEDS) detector (Super-X G2 XEDS system, Thermo Fisher, USA). [0110] The Brunauer–Emmet–Teller (BET) and Barrett-Joyner-Halenda (BJH) methods were utilized to determine the surface area and pore structure of MgO from N2 absorption-desorption data obtained on a Quantachrome Quadrasorb SI (Quantachrome Instruments, Oldelzhauzen, Germany). [0111] X-ray photoelectron spectroscopy (XPS) measurements were performed on a PHI Versa Probe III XPS system (ULVAC-PHI, Japan) using a monochromated Al KD X- ray source (1486.6 eV). The base pressure was 2.8×10í8 Pa. [0112] Temperature programmed desorption (TPD) was performed on an AutosorbiQ apparatus (Quantachrome Instruments, USA) equipped with a thermal conductivity detector (TCD) detector. First, the samples (60 mg) were processed in situ in a 50 mL/min helium (He) flow at 150°C for 30 minutes, then cooled to 50°C. The samples were then exposed to CO2 (20 mL/min) for 120 min at 50°C. The physisorbed CO2 was removed by flushing with a 50 mL/min flow of He for 90 min. TPD was performed in the stream of He at a heating rate of 10°C/min up to 800°C. [0113] Raman spectroscopy was performed using a Raman spectroscope (MacroRam, Horiba Scientific, France). The wavelength was set at 785 nm. By measuring 5 ml of solutions with a syringe at predetermined intervals and filtering the solutions through a syringe filter to remove the catalyst, MEA sorbent samples with various absorption and desorption periods were created. The samples were then put into quartz cuvettes for Raman analysis. 2.1. Preparation of MgO NPs [0114] MgO nanoparticles (MgO NPs) were prepared according to the following non- limiting procedure. Magnesium nitrate hexahydrate (Mg(NO3)2 ā 6H2O, about 25.6 g), as an example magnesium source, was dissolved in deionized (DI) water (about 300 mL) and the resulting solution was kept under constant stirring. PEG 1500 (about 5 g), as an example templating agent, was then added to the solution. [0115] An example base was prepared by dissolving sodium carbonate (Na2CO3, about 15.9 g) in DI water (about 300 mL). While the magnesium salt solution was vigorously stirred within the rate of 100-1,000 rpm or by sonication, or by ultrasonication, the base was added dropwise over a period from 1-10 minutes. The resulting solution was carefully washed with an appropriate solvent (e.g., ethanol) to separate the precipitate from the liquid, and dried at about 80°C for about 12 hours (h). The as-synthesized MgO NPs were then calcined at a desired temperature (about 500°C, about 700°C, about 900°C, or about 1100°C) for a desired period (about 2 h). Calcination resulted in a calcined form of the MgO NPs. The products were named as MgO-500, MgO-700, MgO-900, and MgO-1100, respectively with reference to the calcination temperature. [0116] The production of MgO NPs using the precipitation method can be performed on an industrial scale. Payback Period analysis shows that the investment will experience a profit after three years. Here, if the initial factory is designed to obtain 11,250 kg of MgO NPs daily, the total profit earned is 1,881,184,753 USD in 10 years. 2.2. Compositions for CO2 Capture [0117] The MgO NPs can be utilized for a variety of applications. One non-limiting application is for CO2 capture. For CO2 absorption and desorption experiments, monoethanolamine (MEA) was chosen as an example organic amine. The MgO-NPs can accelerate and/or catalyze both sorption and desorption from the MEA. In some examples, the solution can include one or more suitable additives including, for example, a surfactant, an antifoaming agent, or combinations thereof. The surfactant can be utilized to, for example, minimize agglomeration and sedimentation of MgO nanoparticles in the solution. The antifoaming agent can be utilized to depress foaming and bubbles and thereby facilitate the process of packing, sampling, and testing the solution. [0118] To make a composition, MgO NPs (about 2 wt%) were added into a 20 wt% MEA aqueous solution (about 100 g). In some examples, about 0.1ௗwt% 1-hexadecyl trimethyl ammonium bromide (CTAB, CH3(CH2)15N(CH3)3Br, Chem Impex Int’l Inc., USA) was added to the solutions. In some examples, about 0.1 wt% of Antifoam 204 (Sigma, USA) was added because CTAB produces bubbles when it dissolves in water. In some examples, the wt% of surfactant and antifoaming agent can be the same. In other examples, the wt% can be different. [0119] The resulting MgO solution was stirred using an ultrasonic vibrator (130ௗW, 20 kHz, VCX 130PB, Sonics & Materials Inc., USA) for about 10ௗmin to achieve a stable dispersion and suspension. The prepared MgO solution was determined to have good dispersion stability even after sitting for about 24 h or more. 2.3. CO2 Capture Experiments [0120] Studies on CO2 absorption and desorption were carried out using the apparatus depicted schematically in FIG. 1. The example CO2 capture experimental setup shown in FIG.1 included the following non-limiting elements: a nitrogen (N2) cylinder 101, a mixed gas cylinder 102, a mass flow controller 103, a thermostatic bath 104, a heater/stirrer 105, a reactor 106, a thermocouple 107, a condenser 108, a desiccator 109, a paperless recorder 110, a gas analyzer 111, and a computer 112. The mixed gas cylinder can include gases such as CO2, oxygen (O2), and/or N2, among others. [0121] A magnetically connected stirrer (e.g., the stirrer of heater/stirrer 105) was coupled to a 250 ml glass reactor (e.g., reactor 106). Each sorption test used about 100 g of MEA diluted to about 20 wt% in water. Both with and without catalyst (MgO) tests were run. The concentration (weight percentage) of nano-MgO catalysts was about 2 wt%. The total gas flow rate for the investigations was about 1,500 mL/min. The gas composition for the investigations was about 10 vol% CO2, about 10 vol% O2, and about 80 vol% N2. The CO2 sorption temperature and sorption time for the investigations were about 25°C, and about 3,600 seconds (s), respectively. The CO2 desorption temperature and desorption time for the investigations were about 90°C, and about 3,600 s, respectively. Experiments were repeated three times for each sample. [0122] CO2 absorption experiments were conducted at room temperature (about 25°C) and atmospheric pressure. A total of about 20 wt% MEA solution was prepared by mixing monoethanolamine (about 20 g) with DI water (about 80 g). Predetermined amounts of the ~20 wt% MEA and MgO catalyst were added to the reactor under a stirring rate of about 500 rpm. Simulated flue gas that contained about 10 vol% CO2, about 10 vol% O2, and about 80 vol% N2 was purchased from Praxair (Danbury, CT, USA). Vögtlin (Monterey, CA, USA) RED-Y mass flow controllers (MFC, for example, mass flow controller 103) were used to control the flow of gases from the gas cylinders (for example, N2 cylinder 101 and mixed gas cylinder 102) to the reactor (for example, reactor 106). [0123] A total flow of 1,500 mL/min was used to inject the simulated flue gas into the MEA solution. The CO2 concentration at the outlet gas of the reactor (for example, reactor 106) was measured with an inline gas analyzer (CAI ZPA, CA, USA) (for example, gas analyzer 111), and a data recording unit (e.g., paperless recorder 110 and computer 112) recorded the measured concentration-time profile. The amount of CO2 absorbed into the MEA solution was calculated by integrating the recorded CO2 sorption profiles. The MFC (for example, mass flow controller 103) for the mixed gas was closed after completing the absorption step, which took about 3600 s for fresh and cyclic MEA solutions. CO2 desorption was achieved by gradually heating the spent sorbent obtained from the CO2 sorption step to the desired desorption temperature (for example, about 90 °C). The desorbed CO2 was mixed with the carrier gas (N2) at a flow rate of about 500 mL/min. An inline gas analyzer (for example, gas analyzer 111) measured the CO2 concentration of the gas mixture. CO2 concentrations in the gas mixture and the corresponding temperatures of the spent MEA solution were recorded over the entire CO2 desorption process. The desorption test also took about 3600 s. The cyclic CO2 sorption began when the temperature of the regenerated MEA solution was cooled to about room temperature. 3. Non-Limiting Results and Discussion [0124] FIG. 2 shows XRD patterns of the calcined MgO products calcined at temperatures ranging from about 500°C to about 1100°C. All of the products show five distinct diffraction peaks at (111), (200), (220), (311), and (222). These are indexed to the cubic phase of MgO (periclase) (JCPDS No. 87-0652; space group: Fm3m). No other reflections indicating impurities were observed. [0125] The diffraction peaks were determined to be somewhat broader for the low- temperature calcined MgO-500, whereas the diffraction peaks became sharper for the calcined samples at higher calcination temperatures, for example, MgO-700, MgO-900, and MgO-1100. XRD analyses revealed that the amorphous phase crystallizes to cubic phase MgO at a temperature of about 500°C. [0126] The crystallite size (D, nm) for MgO products can be determined using the Debye–Scherrer formula of Equation 1:
Figure imgf000030_0001
wherein: ^ (nm) is the X-ray radiation wavelength; ȕ is the diffraction peak full width at half maximum (FWHM); and ^ is the Bragg diffraction angle. [0127] The estimated crystallite size was determined to be about 9 nm for MgO-500, about 22 nm for MgO-700, about 48 nm for MgO-900, and about 53 nm for MgO-1100. The average crystallite size increased with an increase in calcination temperature. [0128] The morphology and chemical makeup of the as-produced MgO samples were determined by TEM, STEM, and XEDS analyses. The low-magnification and magnified TEM images of FIG. 3A revealed the synthetic MgO-500 sample’s holey lamellar structure, which is made up of many particles. As shown in the STEM image of FIG. 3B, the interconnected MgO NPs can create a wall with a holey structure, with an estimated particle size of about 8 nm to about 10 nm. FIGS.3G and 3H—the TEM and STEM images of MgO-700—clearly demonstrated that the pore sizes and particle sizes (about 20 nm) can increase with rising temperature. FIGS. 3G and 3H also indicated that the mesh-like structure can be made up of a network of nanowires. High specific surface area mesoporous nanoparticles have been shown to improve the mass transfer between gas and liquid, resulting in strong CO2 absorption capacity. The TEM and STEM images of MgO- 900 (FIGS. 3M and 3N) and MgO-1100 (FIGS. 3S and 3T) show that with a further increase in temperature, the holey lamellar structure disappeared, and MgO NPs grew into individual cubic-shaped particles with a particle size of about 50 nm to about 70 nm. [0129] STEM HAADF and XEDS analysis were used to further analyze the elemental composition of the example MgO NPs. HAADF images and associated element maps of MgO-500 are shown in FIGS. 3C-3F. The holey lamellar structure’s carbon (C), magnesium (Mg), and oxygen (O) distributions are uniform throughout, as seen in the element maps from the HADDF images. When combined with the XRD and XPS results, the images indicated that the MgO product obtained at about 500^ may have insufficient crystallization and may have large amounts of amorphous MgCO3 impurities. The element maps from the HADDF image of MgO-700 (FIGS.3I-3L), MgO-900 (FIGS.3O-3R), and MgO-1100 (FIGS. 3U-3X) show uniform distributions of Mg and O without C indicating that pure single-phase MgO can be formed at about 700^ or higher. MgO-700, MgO- 900, and MgO-1100 were selected for subsequent investigations. [0130] Nitrogen absorption and desorption isotherm curves of example MgO NPs are shown in FIG.4A. The Brunauer–Emmet–Teller (BET) method was used to calculate the specific surface area of the MgO NPs. The Barrett-Joyner-Halenda (BJH) method was used to determine the pore size distribution of the MgO NPs. Selected results are shown in Table 1. Specifically, Table 1 shows the specific surface area, the pore volume, and the average pore size (average pore diameter) of example MgO NPs estimated from N2 absorption-desorption measurements using BET and BJH methods. In Table 1, SBET refers to BET specific surface area, Vt refers to total pore volume, and Dp refers to BJH Desorption average pore diameter (4V/A). Table 1 SBET, Vt, Dp, Sample m2g–1 cm3g–1 nm MgO-700 193.3 0.36 9.2 MgO-900 148.6 0.26 8.0 MgO-1100 124.3 0.15 7.6 [0131] According to the International Union of Pure and Applied Chemistry (IUPAC) classification of porous materials, MgO NPs present typical type IV curves in the range of 0-1.0 relative pressure with a type H3 hysteresis loop. This indicates that the pore structures of the samples were mainly mesopores (about 2 nm < pore diameter < about 50 nm). The specific surface area (about 193.3 m2gí1) and total pore volume (about 0.36 m3gí1) of MgO-700 were calculated from the isotherm. These values are higher than those of MgO-900 (about 148.6 m2gí1 and about 0.26 m3gí1) and MgO-1100 (about 124.3 m2gí1 and about 0.15 m3gí1). The BJH desorption average pore diameter of MgO-700, MgO- 900, and MgO-1100 were determined to be about 9.2 nm, about 8.0 nm, and 7.6 nm, respectively. [0132] The pore size distribution curves of MgO NPs are shown in FIG. 4B, showing that all investigated samples have mesopores that are between about 2 nm and about 50 nm. Relative to MgO-900 and MgO-1100, MgO-700 has a high proportion of mesopores between about 5 nm and about 15 nm, which is consistent with the TEM images of FIGS. 3G and 3H. While not wishing to be bound by any theory, this finding can be a result of the unique structure of the mesh-like, interconnected MgO structure, whose fundamental components are primary nanoparticles. [0133] XPS was used to determine how the calcination temperature affected the composition of the MgO surface. FIG. 5A shows a XPS survey spectrum associated with MgO-700, MgO-900, and MgO-1100 samples. MgO and O photoelectron peaks were observed, and the three sample peaks were noted as being comparable, which was in agreement with the XRD findings. [0134] The Mg 2p peak high-resolution spectra of the three samples are presented in FIG.5B. The Mg 2p spectra of MgO-700 were divided into two peaks at binding energies of about 50.1 eV and about 48.6 eV, corresponding to the existence of Mg(OH)2 and MgO, respectively. Quantitative analysis of the XPS data was utilized to calculate the corresponding molar percentage of Mg species. This XPS data of the MgO NPs is shown in Table 2. It was determined that the composition of Mg(OH)2 rapidly decreases as the temperature rises (for example, the Mg(OH)2 area% for MgO-700 was determined to be about 37.8, while the Mg(OH)2 area% for MgO-900 was determined to be about 2.4. [0135] FIG. 5C shows the high-resolution spectra of O 1s for the three samples. The binding energies of about 528.9 eV and about 530.8 eV were associated with the lattice oxygen of metal oxides (Olat) and surface-absorbed oxygen species (Oads), respectively. The ratio of Oads to Olat was utilized to calculate the relative oxygen vacancy concentration. Table 2 also reports the relative oxygen vacancy concentration for the example MgO NPs. The order in which the ratio of relative oxygen vacancy concentration for MgO was determined as follows: MgO-700 > MgO-900 > MgO-1100. This result suggested that a rise in calcination temperature can result in a fall in oxygen vacancy concentration. Such observations fit well with the surface area order, suggesting that surface oxygen vacancies participate in various chemical reactions that are metal oxide-catalyzed. Table 2 XPS-Mg2p XPS-O1s Samples
Figure imgf000033_0001
MgO-700 62.2 37.8 57.2 42.8 1.3 MgO-900 97.6 2.4 28.7 71.3 0.4 MgO-1100 100 0 15.1 84.9 0.2 [0136] In order to better understand the chemical activity of the MgO NPs, different basic sites—weak basic, medium basic, and strong basic—were further characterized by temperature programmed desorption (TPD)-CO2. FIG. 6 demonstrates how the three temperature ranges that make up the TPD profile can be split. Ball and stick models are also shown in FIG.6 illustrating CO2 absorbed species over the weak, medium, and strong basic sites. These CO2 absorbed species can be bicarbonate, bidentate carbonate, and unidentate carbonate, respectively. [0137] With reference to FIG. 6, the temperature range of about 50^ to about 175^ is responsible for weak basic sites and were attributed to the surface hydroxyl groups. The temperature range of about 175^ to about 400^ is responsible for medium basic sites and were attributed to the oxygen in Mg2+ and O2í pairs. Strong basic sites are typically linked to the low coordinate oxide sites at higher temperatures (about 400^ to about 800°C). CO2 absorption over weak and medium basic sites may occur as bicarbonate and bidentate carbonate species while CO2 absorption over strong basic sites may occur as unidentate species. Table 3 shows non-limiting TPD-CO2 data for the MgO samples. In Table 3, the values under the column headers weak basic sites, medium basic sires, and strong basic sites refer to the CO2 desorption peak area of the various basic sites. “TBS” refers to total basic sites. The values under the column header TBS refer to the total CO2 desorption peak area of various basic sites. Basic site density is equal to the TBS value divided by the BET surface area value (TBS/BET surface area). Table 3 Weak basic Medium Strong Basic sites Samples TBS sites basic sites basic sites density MgO-700 1,503 39,841 1,576 42,920 222 MgO-900 975 8,152 1,058 10,185 68.5 MgO-1100 854 6,627 923 8,404 67.6 [0138] The results in Table 3 show three separate MgO sample concentrations of the weak, medium, and strong basic sites differ in the pattern of MgO-700 > MgO-900 > MgO- 1100. Overall, the results presented in Table 3 agree well with the oxygen vacancy concentration order as determined by XPS. [0139] The inset of FIG. 6 shows that MgO-700 has a higher amount of weakly basic sites below about 90^. This observation is based on the area under the MgO-700 being higher than those obtained with the other MgO nanoparticles. Because catalytic reactions for MEA capture of CO2 is initiated by the zwitterion intermediate, the higher concentration of basic sites present in MgO-700 can enhance its catalytic activity. [0140] While not wishing to be bound by any theory, a proposed zwitterion mechanism is further described below to illustrate, for example, how CO2 and MEA may react. FIG. 7A displays the function of the Zwitterion mechanism. The zwitterion mechanism includes the creation of a carbamate (MEACOOí) via a zwitterion intermediate, followed by the hydrolysis-based formation of bicarbonate (HCO3 í). [0141] While not wishing to be bound by any theory, a possible catalytic sorption- desorption CO2 mechanism of MgO catalysis is proposed in FIG. 7B. The MgO catalyst can provide Lewis-base sites during the catalysis process. One of the double bonds between carbon and oxygen (C=O) of CO2 can break because the link formed between the MgO and CO2 violates the carbon octet rule. As a result, the oxygen (from the C=O) can receive a partial charge, which can increase the reactivity of CO2 and MEA. The nitrogen in MEA can eventually break the MgO-CO2 link, which transfers its lone electrons to the remaining MgO-CO2 bond. Vacancies can more readily bind CO2 than typical oxide sites, which can help with their dissociation. Thus, the MgO NPs can be beneficial in forming a zwitterion during CO2 sorption and desorption. [0142] The as-prepared MgO NPs (MgO-700 NPs, MgO-900 NPs, and MgO-1100 NPs) were evaluated for CO2 absorption at about 298 K (FIGS. 8A-8C). All tests were conducted with a dosage of about 2 wt% MgO NPs. Higher sorption efficiency and quicker CO2 sorption are characteristics of sorbents with longer effective periods. [0143] CO2 breakthrough curves are shown in FIG. 8A for about 20 wt% MEA both with and without MgO NPs. The U.S. Department of Energy (DOE) aims to capture 90% of the CO2 in flue gas, and when MgO NPs were added, the effective sorption period was greatly extended. According to FIG.8A, without the added catalyst, the MEA solution can only absorb about 4.2 mmol of CO2 with a breakthrough time (the time with 90% CO2 capturing efficiency) of about 50 seconds (s). In contrast, the sorbent with MgO-700 NPs, MgO-900 NPs, and MgO-1100 NPs can absorb about 158.1 mmol of CO2, about 139.8 mmol of CO2, and about 128.5 mmol of CO2, respectively. Also, the corresponding breakthrough times are about 1550 s, about 1368 s, and about 1276 s, respectively. For comparison, when MEA is used with MgO-700 NPs, the process increases the breakthrough time by about 3,000% under the conditions tested. Likewise, this process is also able to increase the CO2 absorption capacity within the breakthrough time by about 3,660% under the conditions tested. [0144] As shown in FIG. 8C and FIG. 9A, the MgO NPs catalysts have significantly improved the CO2 absorption capacity of MEA within the overall capture times. Specifically, MgO-700 NPs shows the highest absorption capacity (about 212.6 mmol), followed by MgO-900 NPs (about 210.5 mmol), and MgO-1100 NPs (about 207.5 mmol) under the conditions tested. The amount of CO2 absorbed without using the MgO NPs is about 160.7 mmol. From a comparison of samples with and without MgO NPs, the CO2 absorption capacity of MEA with MgO-700 NPs increased by about 31.8%. [0145] The catalytic effect of MgO NPs on CO2 desorption was examined with the used MEA sorbent obtained after about 3,600 seconds of CO2 sorption. A considerable improvement has been achieved, as shown by the curve of the desorption rate in FIG. 8B. For example, adding the MgO NP catalyst increases the CO2 desorption to about 8,740% at about 200 s (FIG.8B inset). The inset of FIG.9B shows the percentage increase in CO2 desorption quantity as a result of using MgO NPs described herein. The accumulated desorbed CO2 concentration of the catalyzed spent MEA with MgO NPs at about 260 s was about 2,290% greater than that of the uncatalyzed spent MEA when compared to the CO2 desorption of the uncatalyzed spent MEA. The accumulation curve of CO2 desorption (FIG.8C and FIG.9B) shows that the MgO NPs calcined at different temperatures can play a significant role. [0146] Without a catalyst, only 90.5 mmol of CO2 could be desorbed after 3600 s by the aqueous MEA solution. The cumulative desorption amounts of MgO-700, MgO-900, and MgO-1100 are about 113.7 mmol, about 108.3 mmol, and about 105.5 mmol, respectively under the conditions tested. MgO-700 has the highest desorption capacity. The amount of CO2 absorbed and desorbed on MgO NPs increased in the order of MgO- 1100 < MgO-900 < MgO-700. The increased specific surface area, oxygen vacancies, and basic sites of MgO-700 in comparison to the other samples may help explain this tendency. [0147] Table 4 provides a summary of absorption enhancement performance of CO2 absorption/desorption for an example absorbent (Ex. 1). Table 4 also shows comparative examples absorbents from recent studies on the improvement of CO2 absorption driven by nanoparticles. Maximum enhancement ratio of absorption is calculated as the ratio of the maximum amount of CO2 sorbed with the use of nanoparticles to that without the use of nanoparticles. The significantly improved CO2 capture performance of mesoporous MgO described herein may be attributed to its surface being enhanced with oxygen vacancies and basic sites. Table 4 Maximum Size and Example Absorbent Nanoparticles enhancement ratio concentration of Abs. H2O and MEA 20 nm, Ex.1 0%, Abs. 25^) M 1.32 (2 gO 2 wt% H2O and MEA 20 nm, C.Ex.1 TiO2 1.16 (20%, Abs. 30^) 0.6 wt% H2O and MEA 20 nm, C.Ex.2 1.19 (30%, Abs. 30^) TiO2 0.6 wt% H2O and MEA 20 nm, C.Ex.3 ) Mg 1.12 (30%, Abs. 30^ O 0.6 wt% H2O and MEA 15 nm, C.Ex.4 SiO2 1.12 (30%, Abs. 40^) 0.06 wt% H2O and MEA 15 nm, C.Ex.5 1.11 (30%, Abs. 40^) Al2O3 0.06 wt% H2O and MEA 15 nm, C.Ex.6 1.14 (30%, Abs. 40^) TiO2 0.06 wt% H2O and MEA 20 nm, C.Ex.7 %, Abs. 35^) T 1.14 (30 iO2 0.8 wt% H2O and MEA 20 nm, C.Ex.8 1 , Abs. 35^) Al O .04 (30% 2 3 0.6 wt% H2O and MEA 15 nm, C.Ex.9 SiO2 1.10 (30%, Abs. 35^) 0.06 wt% H2O and MEA 20 nm, C.Ex.10 Al 1.08 (30%, Abs. 35^) 2O3 0.02 wt% [0148] For practical industrial applications, the long-term stability and regeneration of CO2 absorbents are considerations. As shown in FIG.10A, the time it takes for MEA with MgO NPs absorption to achieve about 90% CO2 capture remained at about 750 s from the first to the tenth cycle, whereas the breakthrough time for MEA solution without an added catalyst was only about 50 s. This result indicates that MgO NP catalysts described herein can increase the breakthrough time by about 1400%. [0149] As illustrated in FIGS. 11A-11C, the cumulative absorbed CO2 quantity of the sample with the MgO-700 NPs is higher than that without MgO-700 NPs. For the 20 wt% MEA solution with MgO-700 NPs, the first-tenth cycle curves and the zeroth cycle curve almost overlap in the first 800s. Still, for the MEA solution without a catalyst, the kinetics of the first-tenth cycle curves drop significantly. [0150] As shown in FIGS. 11F-11H, after the catalyst was added, the cumulative amount in the desorption cycle was close to the sample without the catalyst. However, the desorption rate of the sample with the catalyst is significantly higher (FIGS. 11D-11E). The cyclic CO2 absorption-desorption capabilities of 20 wt % MEA solution catalyzed by about 2 wt% MgO NPs for 50 consecutive runs are shown in FIG.10B. The data indicates that the MgO nanoparticles described herein have good long-cycling stability with about 97.2% absorption capacity retention after 50 cycles. The results also indicate that MgO- 700 NPs may maintain, recover, and regenerate the active sites after being subjected to 50 cycles. It was also found that the MgO-700 NPs can maintain consistent efficiency after repeated use. MgO is an eco-friendly and nontoxic material widely used in various industries. Developing recyclable technologies for metal resources can be a cost-effective way to avoid repeated metallurgical processes and reduce greenhouse gas emissions. In the recycled process, the MgO nanoparticles can be recycled by filtration, and then additional washing steps for recycled MgO can be performed. This wastewater from other washing steps can be reused in CO2 absorbents. [0151] Raman spectroscopy was utilized to confirm that MgO NPs had a catalytic effect on the absorption and desorption of CO2. Raman spectra of MEA aqueous solutions with and without 2 wt% MgO-700 NPs were examined to observe the effect of the catalyst on the absorption step. The findings are shown in FIG. 12A and FIG. 13A. The peaks at about 1012 cmí1, about 1063 cmí1, and about 1153 cmí1 represent the C–OH stretch of HCO3 í, the C–O stretch of
Figure imgf000039_0001
and the C–N stretch of RNHCO2 í, respectively. When using the MgO-700 NPs catalyst, RNHCO2 í production can reach its peak height more quickly than without using the catalyst. Additionally, the peak intensity of HCO3 í after the first 20 minutes of catalyzed CO2 sorption can be higher than that achieved without the MgO-700 NPs catalyst. [0152] In the case of desorption (FIG. 12B and FIG. 13B), the peak intensities of HCO3 í and RNHCO2 í can gradually decrease with the CO2 desorption time. Likewise, the CO3 2í peak intensity of the catalytic spent MEA solution can decrease slower than that of the uncatalyzed one. However, after MgO-700 NPs were added to the MEA solution, all of the HCO3 í, CO3 2í, and RNHCO2 í can have their peak heights decreased at higher rates. For example, within just about 30 minutes, the peak HCO3 í intensity in the MEA solution with MgO NPs can decrease significantly. This result suggests that the MgO-700 NPs can be responsible for the substantial catalytic increase of CO2 desorption. Raman spectral observations demonstrate the significant catalytic effect MgO-700 NPs can have on CO2 absorption and desorption kinetics. [0153] Embodiments described herein generally relate to processes for forming magnesium oxide particles and compositions thereof. Embodiments described herein also generally relate to CO2 absorption, CO2 desorption, and/or CO2 capture processes. [0154] Overall, embodiments of the present disclosure provide a facile, efficient, and scalable co-precipitation-calcination process using PEG (e.g., PEG 1500) as an example soft template to synthesize mesoporous MgO NPs at various temperatures (about 500°C, about 700°C, about 900°C, and about 1100°C). The MgO surface structure can be nonstoichiometric due to its distinctive shape, which includes several surface hydroxyl groups and lattice defects from its calcination process. Strong catalytic activity can be provided by oxygen vacancies, which is supported by basic sites from the TPD-CO2 investigations that have varying strengths and relative concentrations. Compared to the system without a catalyst, MgO NPs can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by about 3,000% or more and can increase the CO2 absorption capacity within the breakthrough time by about 3,660% or more, and increased the maximum CO2 desorption rate by about 8,740% or more at about 200 s. As a result, CO2 activation tests showed that the MgO NPs can maintain steady efficiency even after repeated usage with no discernible decline in the catalytic impact of MgO. These results suggest that MgO NPs effectively improve MEA-based CO2 absorption and desorption efficiencies. Embodiments Listing [0155] The present disclosure provides, among others, the following embodiments, each of which can be considered as optionally including any alternate embodiments: [0156] Clause A1. A composition for absorbing or desorbing carbon dioxide (CO2), the composition comprising: an organic amine; and magnesium oxide (MgO). [0157] Clause A2. The composition of Clause A1, wherein the MgO is in the form of particles, the particles having: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; a specific surface area that is about 300 m2g–1 or more, such as from about 300 m2g–1 to about 800 m2g–1; a total pore volume that is about 2 cm3g–1 or less; or combinations thereof. [0158] Clause A3. The composition of Clause A1 or Clause A2, wherein the MgO is in the form of particles, the particles having: an average particle size that is from 8 nm to about 70 nm; an average pore diameter that is from about 2 nm to about 20 nm; a specific surface area that is about 500 m2g–1 or less, such as about 250 m2g–1 or less; a total pore volume that is about 1 cm3g–1 or less; or combinations thereof. [0159] Clause A4. The composition of any one of Clauses A1-A3, further comprising water. [0160] Clause A5. The composition of any one of Clauses A1-A4, wherein an amount of the MgO in the composition is about 5 wt% (50,000 ppm) or less based on a total weight of the composition. [0161] Clause A6. The composition of any one of Clauses A1-A5, wherein an amount of the MgO in the composition is about 2.5 wt% (25,000 ppm) or less based on a total weight of the composition. [0162] Clause A7. The composition of any one of Clauses A1-A6, wherein the organic amine comprises a primary amine compound, a secondary amine compound, a tertiary amine compound, or combinations thereof. [0163] Clause A8. The composition of any one of Clauses A1-A7, wherein the organic amine comprises monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), or combinations thereof. [0164] Clause A9. The composition of any one of Clauses A1-A8, wherein the organic amine comprises a polyethylene amine, the polyethylene amine comprising diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA), polyethyleneimine (PEI), or combinations thereof. [0165] Clause A10. The composition of any one of Clauses A1-A9, further comprising one or more additives, the one or more additives comprising a surfactant, an antifoaming agent, or combinations thereof. [0166] Clause B1. A process for making a composition for absorbing or desorbing carbon dioxide (CO2), the process comprising: ultrasonically treating a mixture comprising MgO particles, organic amine, and water; and optionally introducing an additive to the mixture to form the composition of any one of Clauses A1-A10. [0167] Clause B2. The process of Clause B1, wherein the additive comprises a surfactant, an antifoaming agent, or combinations thereof. [0168] Clause C1. A process for capturing carbon dioxide (CO2) from a gas stream, comprising: introducing a gas stream with a composition under absorption conditions, the gas stream comprising CO2, the composition comprising: an organic amine, an ion, thereof, or combinations thereof; magnesium oxide (MgO); and optionally water, an ion thereof, or a combination thereof; and forming a CO2-enriched composition. [0169] Clause C2. The process of Clause C1, wherein the composition comprises the composition of any one of Clauses A1-A10 and/or the composition made according to any one of Clauses B1-B2. [0170] Clause C3. The process of Clause C1 or Clause C2, wherein at least a portion of the composition is ultrasonically pretreated. [0171] Clause D1. A process for desorption of carbon dioxide (CO2) from a CO2- enriched composition, the process comprising: heating a CO2-enriched composition under desorption conditions, the CO2- enriched composition comprising: an organic amine, an ion thereof, or a combination thereof; magnesium oxide (MgO); and optionally water, an ion thereof, or a combination thereof; and separating CO2 from the CO2-enriched composition to form a CO2-depleted composition. [0172] Clause E1. A process for capturing carbon dioxide (CO2) from a gas stream, comprising: contacting the gas stream with a composition, under absorption conditions, in an absorption unit to form a CO2-enriched composition, the gas stream comprising CO2, the composition comprising the composition of any one of Clauses A1-A10 and/or the composition made according to any one of Clauses B1-B2; passing the CO2-enriched composition to a desorption unit; heating at least a portion of the CO2-enriched composition in the desorption unit; separating CO2 from the CO2-enriched composition to form a CO2-depleted composition; and regenerating the composition from at least a portion of the CO2-depleted composition, recycling at least a portion of the CO2-depleted composition to the absorption unit, or both. [0173] Clause F1. A process for forming magnesium oxide particles, comprising: forming a mixture comprising a magnesium source, a templating agent, a base, and a solvent; and drying and/or calcining the mixture at a temperature of about 450°C to about 1200°C to form magnesium oxide particles. [0174] Clause F2. The process of Clause F1, wherein: the templating agent comprises a polyethylene glycol; the base comprises an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof; or combinations thereof. [0175] Clause F3. The process of Clause F1 or Clause F2, wherein the magnesium oxide particles have: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; a specific surface area that is about 300 m2g–1 or more, such as from about 300 m2g–1 to about 800 m2g–1, or about 500 m2g–1 or less, or about 250 m2g–1 or less; a total pore volume that is about 2 cm3g–1 or less; or combinations thereof. [0176] Clause G1. A process for forming mesoporous magnesium oxide particles, the process comprising: forming a mixture comprising a magnesium source and a templating agent in a liquid; introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles; separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles; and calcining the as-synthesized form of the mesoporous magnesium oxide particles under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles. [0177] Clause G2. The process of Clause G1, wherein the introducing the base to the mixture to precipitate the as-synthesized form of the mesoporous magnesium oxide particles comprises sonicating the mixture while introducing the base to the mixture. [0178] Clause G3. The process of Clause G1 or Clause G2, wherein the calcination conditions comprise a calcination temperature that is from about 450°C to about 1200°C. [0179] Clause G4. The process of any one of Clauses G1-G3, wherein: the base comprises an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof; and/or the liquid is water. [0180] Clause G5. The process of any one of Clauses G1-G4, wherein, when the base comprises the alkali metal carbonate, the alkali metal carbonate comprises lithium, sodium, or potassium. [0181] Clause G6. The process of any one of Clauses G1-G5, wherein the base comprises sodium carbonate (Na2CO3). [0182] Clause G7. The process of any one of Clauses G1-G6, wherein the templating agent comprises a glycol. [0183] Clause G8. The process of any one of Clauses G1-G7, wherein the templating agent comprises a polyethylene glycol. [0184] Clause G9. The process of any one of Clauses G1-G8, wherein a weight ratio of the magnesium source to the templating agent is from about 10:1 to about 1:1, such as from about 8:1 to about 2:1, such as from about 6:1 to about 4:1, such as about 5:1. [0185] Clause G10. The process of any one of Clauses G1-G9, wherein the calcined form of the mesoporous magnesium oxide particles has a specific surface area that is from about 100 m2g–1 to about 800 m2g–1, or about 300 m2g–1 or more, or from about 300 m2g–1 to about 800 m2g–1, or about 500 m2g–1 or less. [0186] Clause G11. The process of Clause 10, wherein the calcined form of the mesoporous magnesium oxide particles has: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; a total pore volume that is about 2 cm3g–1 or less; or combinations thereof. [0187] Clause G12. The process of Clause 10 or Clause 11, wherein the calcined form of the mesoporous magnesium oxide particles has: a specific surface area that is from about 100 m2g–1 to about 400 m2g–1; an average particle size that is from about 8 nm to about 70 nm; an average pore diameter that is from about 2 nm to about 20 nm; a total pore volume that is about 1 cm3g–1 or less; or combinations thereof. [0188] Clause H1. A process for forming mesoporous magnesium oxide particles, the process comprising: forming a mixture comprising a magnesium source and a templating agent in a liquid; introducing an aqueous base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles, the aqueous base comprising an alkali metal carbonate; separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles; and calcining the as-synthesized form of the mesoporous magnesium oxide particles at a temperature that is from about 450°C to about 1200°C to form a calcined form of the mesoporous magnesium oxide particles, the calcined form of the mesoporous magnesium oxide particles having a specific surface area that is from about 100 m2g–1 to about 800 m2g–1. [0189] Clause H2. The process of Clause H1, wherein the specific surface area of the calcined form of the mesoporous magnesium oxide particles is from about 100 m2g–1 to about 400 m2g–1. [0190] Clause I1. A process for capturing carbon dioxide (CO2), the process comprising: introducing or contacting a composition with a gas stream comprising CO2, the composition comprising the mesoporous magnesium oxide particles made according to any one of Clauses G1-G12 or H1-H2. [0191] Clause J1. A process for capturing carbon dioxide (CO2) from a gas stream, comprising: introducing a gas stream comprising CO2 with a composition under absorption conditions, the composition comprising: an organic amine; calcined mesoporous magnesium oxide particles having a specific surface area that is from about 100 m2g–1 to about 800 m2g–1; and optionally water; and forming a CO2-enriched composition. [0192] Clause J2. The process of Clause J1, wherein at least a portion of the composition is ultrasonically pretreated prior to introducing the gas stream to the composition. [0193] Clause J3. The process of Clause J1 or Clause J2, wherein an amount of the calcined mesoporous magnesium oxide particles in the composition is from greater than 0 wt% to less than about 5 wt% based on a total wt% of the composition. [0194] Clause J4. The process of any one of Clauses J1-J3, wherein the organic amine in the composition comprises monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA), polyethyleneimine (PEI), or combinations thereof. [0195] Clause J5. The process of any one of Clauses J1-J4, wherein the composition further comprises one or more additives, the one or more additives comprising a surfactant, an antifoaming agent, or combinations thereof. [0196] Clause J6. The process of any one of Clauses J1-J5, wherein the calcined mesoporous magnesium oxide particles have: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; or combinations thereof. [0197] All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures to the extent they are not inconsistent with this text. As is apparent from the foregoing general description and the specific embodiments, while forms of the embodiments have been illustrated and described, various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, it is not intended that the present disclosure be limited thereby. Likewise, the term “comprising” is considered synonymous with the term “including.” Likewise whenever a composition, an element, a group of elements, or a method is preceded with the transitional phrase “comprising,” it is understood that we also contemplate the same composition, method, or group of elements with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “Is” preceding the recitation of the composition, element, elements, or method, and vice versa, such as the terms “comprising,” “consisting essentially of,” “consisting of” also include the product of the combinations of elements listed after the term. [0198] In the foregoing, reference is made to embodiments of the disclosure. However, it should be understood that the disclosure is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether related to different embodiments or not, is contemplated to implement and practice the disclosure. Furthermore, although embodiments of the disclosure may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the disclosure. Thus, the foregoing aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the disclosure” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s). [0199] For purposes of this present disclosure, and unless otherwise specified, all numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and consider experimental error and variations that would be expected by a person having ordinary skill in the art. For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. For example, the recitation of the numerical range 1 to 5 includes the subranges 1 to 4, 1.5 to 4.5, 1 to 2, among other subranges. As another example, the recitation of the numerical ranges 1 to 5, such as 2 to 4, includes the subranges 1 to 4 and 2 to 5, among other subranges. Additionally, within a range includes every point or individual value between its end points even though not explicitly recited. For example, the recitation of the numerical range 1 to 5 includes the numbers 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, among other numbers. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited. [0200] As used herein, the indefinite article “a” or “an” shall mean “at least one” unless specified to the contrary or the context clearly indicates otherwise. For example, embodiments comprising “an organic amine” include embodiments comprising one, two, or more organic amines, unless specified to the contrary or the context clearly indicates only one organic amine is included. [0201] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. [0202] Certain molecules disclosed herein may contain one or more ionizable groups [groups from which a proton can be removed (e.g., –COOH) or added (e.g., amines) or which can be quaternized (e.g., amines)]. All possible ionic forms of such molecules and salts thereof are intended to be included individually in the disclosure herein. [0203] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is: 1. A process for forming mesoporous magnesium oxide particles, the process comprising: forming a mixture comprising a magnesium source and a templating agent in a liquid; introducing a base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles; separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles; and calcining the as-synthesized form of the mesoporous magnesium oxide particles under calcination conditions to form a calcined form of the mesoporous magnesium oxide particles.
2. The process of claim 1, wherein the introducing the base to the mixture to precipitate the as-synthesized form of the mesoporous magnesium oxide particles comprises: sonicating the mixture while introducing the base to the mixture.
3. The process of claim 1, wherein the calcination conditions comprise a calcination temperature that is from about 450°C to about 1200°C.
4. The process of claim 1, wherein: the base comprises an alkali metal carbonate, an alkaline earth metal carbonate, or combinations thereof; and the liquid comprises water.
5. The process of claim 4, wherein, when the base comprises the alkali metal carbonate, the alkali metal carbonate comprises lithium, sodium, or potassium.
6. The process of claim 1, wherein the base comprises sodium carbonate (Na2CO3).
7. The process of claim 1, wherein the templating agent comprises a glycol.
8. The process of claim 1, wherein the templating agent comprises a polyethylene glycol.
9. The process of claim 1, wherein a weight ratio of the magnesium source to the templating agent is from about 10:1 to about 1:1.
10. The process of claim 1, wherein the calcined form of the mesoporous magnesium oxide particles has a specific surface area that is from about 100 m2g–1 to about 800 m2g–1.
11. The process of claim 10, wherein the calcined form of the mesoporous magnesium oxide particles has: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; a total pore volume that is about 2 cm3g–1 or less; or combinations thereof.
12. The process of claim 10, wherein the calcined form of the mesoporous magnesium oxide particles has: a specific surface area that is from about 100 m2g–1 to about 400 m2g–1; an average particle size that is from about 8 nm to about 70 nm; an average pore diameter that is from about 2 nm to about 20 nm; a total pore volume that is about 1 cm3g–1 or less; or combinations thereof.
13. A process for forming mesoporous magnesium oxide particles, the process comprising: forming a mixture comprising a magnesium source and a templating agent in a liquid; introducing an aqueous base to the mixture to precipitate an as-synthesized form of the mesoporous magnesium oxide particles, the aqueous base comprising an alkali metal carbonate; separating the liquid from the as-synthesized form of the mesoporous magnesium oxide particles; and calcining the as-synthesized form of the mesoporous magnesium oxide particles at a temperature that is from about 450°C to about 1200°C to form a calcined form of the mesoporous magnesium oxide particles, the calcined form of the mesoporous magnesium oxide particles having a specific surface area that is from about 100 m2g–1 to about 800 m2g–1.
14. The process of claim 13, wherein the specific surface area of the calcined form of the mesoporous magnesium oxide particles is from about 100 m2g–1 to about 400 m2g–1.
15. A process for capturing carbon dioxide (CO2) from a gas stream, the process comprising: introducing a gas stream comprising CO2 with a composition under absorption conditions, the composition comprising: an organic amine; calcined mesoporous magnesium oxide particles having a specific surface area that is from about 100 m2g–1 to about 800 m2g–1 and an average particle size that is from about 5 nm to about 100 nm; and optionally water; and forming a CO2-enriched composition.
16. The process of claim 15, wherein at least a portion of the composition is ultrasonically pretreated prior to introducing the gas stream to the composition.
17. The process of claim 15, wherein an amount of the calcined mesoporous magnesium oxide particles in the composition is from greater than 0 wt% to less than about 5 wt% based on a total wt% of the composition.
18. The process of claim 15, wherein the organic amine in the composition comprises monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diisopropanolamine (DIPA), monomethyl-ethanolamine (MMEA), methyldiethanolamine (MDEA), diethyl-monoethanolamine (DEMEA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), tetraacetylethylenediamine (TAED), polyethylenehexamine such as pentaethylenehexamine (PEHA), polyethyleneimine (PEI), or combinations thereof.
19. The process of claim 15, wherein the composition further comprises one or more additives, the one or more additives comprising a surfactant, an antifoaming agent, or combinations thereof.
20. The process of claim 15, wherein the calcined mesoporous magnesium oxide particles have: an average particle size that is from about 5 nm to about 100 nm; an average pore diameter that is from about 2 nm to about 50 nm; or combinations thereof.
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