One of the critical and emerging needs for sustainable energy production is the development of novel integrated approaches for the capture, conversion, and storage of CO 2 . In this context, carbon mineralization, which is a thermodynamically downhill route for the accelerated conversion of CO 2 to water-insoluble and stable calcium and magnesium carbonates, is a sustainable approach for permanently storing CO 2 . However, one of the challenges with carbon mineralization has been the need for higher concentrations of CO 2 to accelerate the formation of calcium and magnesium carbonates. In this study, we propose a direct integrated approach in which amine-bearing solvents, such as monoethanolamine (MEA), and alkaline Ca-bearing solids, such as calcium oxide and calcium silicate, are reacted in a slurry reaction system in two modes. These two modes involve in situ changes in the aqueous chemistry to facilitate the capture of CO 2 using MEA and the release of CO 2 into the aqueous phase to produce higher conversions of calcium carbonate. In the first mode, continuous CO 2 flow at 1 atm is provided such that MEA in the aqueous phase captures CO 2 and supplies the captured carbon-bearing species for reaction with dissolved calcium. In the second mode, MEA pre-loaded with CO 2 was introduced into the system without a continuous supply of CO 2 . Complete conversion of calcium oxide to calcium carbonate was achieved using both modes. Further, the extent of carbon mineralization achieved with calcium silicate was 36% in mode 1 as opposed to 20% in mode 2 at 50 °C for a reaction time of 3 h. These data suggested that amine-bearing solvents undergo continuous looping between the CO 2 -loaded and release states, which facilitate the accelerated conversion of calcium-bearing oxides and silicates to calcium carbonate. The formation of calcium carbonate and calcium hydroxide phases was noted when less than complete conversions of calcium oxide were achieved. Calcium carbonate was the only phase formed on the complete conversion of calcium oxide and the carbon mineralization of carbon dioxide.

No abstract

Determining the structure of nanoconfined fluids is essential for predicting the fate of these fluids in subsurface geologic formations with nanoporous features and for engineering novel nanoporous materials for storing compressed gases. In this study, we probe the structure of nanoconfined methane at pressures in the range of 15−100 bar using in situ small-angle neutron scattering (SANS) measurements and molecular dynamics (MD) simulations. The structure of methane is probed in MCM-41 and SBA-15 with cylindrical pores and diameters of 3.3 and 6.8 nm, respectively. In situ SANS measurements and MD simulations showed that the confined methane molecules are organized in a core−shell structure, with the shell arising from the adsorption of methane molecules on the silica surface. The shell thicknesses of the adsorbed deuterated methane (CD 4 ) molecules in MCM-41 obtained by SANS measurements are 1.4

No abstract

Rapid scientific advancements are needed to remove CO 2 from our emissions. In this context, novel molecularly integrated pathways to capture and remove CO 2 as environmentally benign and solid inorganic carbonates are needed. In this study, single-step integrated CO 2 capture and carbonate formation pathways with the inherent regeneration of the aqueous solvents for CO 2 capture are reported. The effectiveness of solvents, such as monoethanolamine (MEA), sodium glycinate (NaGly), 2-amino-2-methylpropanol (AMP), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), on the carbon mineralization of CaO, CaSiO 3 , and MgO is investigated. Experiments are performed at solvent concentrations of 0, 0.5, 1.0, and 2.5 equiv mol/L at 75 °C, p CO 2 of 1 atm with 15 wt % solid, and a reaction time of 3 h in a continuously stirred environment. The highest extents of carbon mineralization of CaO, CaSiO 3 , and MgO are 98.9% at 5 M MEA, 43.40% at 2 M AMP, and 87.50% at 1 M NaGly. High concentrations of aqueous solvents, such as AMP and DBU, exceeding 1 M inhibit carbon mineralization due to the formation of viscous, gel-like fluidic environments that limit transport behavior. Stable calcite and metastable aragonite and vaterite phases result from the carbon mineralization of CaO and CaSiO 3 materials. Metastable hydrated magnesium carbonate phases, such as MgCO 3 •3H 2 O (nesquhonite), MgCO 3 •5H 2 O (lansfordite), and hydromagnesite [Mg 5 (CO 3 ) 4 (OH) 2 •4H 2 O], result from the carbon mineralization of MgO. Overall, significant enhancement in carbon mineralization is achieved using integrated CO 2 capture and carbon mineralization routes with the inherent regeneration of the solvent, as opposed to the base case, where only water is used.

Aqueous amine solvents (e.g., monoethanolamine) coupled with reactive alkaline sorbents (e.g., MgO) favor low temperature CO2 removal as solid carbonates.

Various pathways to accelerate the recovery of hydrocarbons from unconventional subsurface environments have been proposed, including the use of high-temperature fluids. However, the influence of temperature on the structural and microstructural changes in complex subsurface materials characterized by compositional and morphological heterogeneity are not very well understood. In this study, in operando ultrasmall angle, small angle, and wide-angle X-ray scattering (USAXS/SAXS/WAXS) measurements were performed to link the structural and morphological changes in shale when heated from 30 to 1150 °C. The structural changes observed from the wide-angle X-ray scattering measurements were complemented by the changes in the porosity, particle size, and surface morphology. Overall, the combined USAXS/SAXS measurements showed enhanced smoothness in the pore–solid interface on heating. The dehydroxylation of illite and calcination of calcium carbonate were noted prior to the formation of denser and sintered silicate and alumino-silicate phases such as Mg2SiO4 (forsterite), Fe0.3Mg0.7(SiO3) (enstatite), and Al2.35Si0.64O4.82 (mullite).

Determining the organization of CO2 molecules confined in nanoporous environments is essential for unlocking our understanding of the fate of CO2 stored in nanoporous materials. In this study, we investigate...