Search

The success of CO2mineralization as a potential solution for reducing carbon emissions hinges on understanding chemical interactions between basaltic minerals and CO2-charged fluids. This study provides a detailed analysis of olivine dissolution in CO2-water mixtures at 90 and 150 °C, 2–9 MPa, and for 8 and 24 h, in both water- and CO2-dominant conditions. By using olivine crystal sections instead of powders, surface agitation is prevented, closing the gap between laboratory studies and natural settings. Surface chemistry, texture, and cross-sectional properties were examined pre- and postreaction using a multiscale approach combining spectroscopic and imaging techniques. Results show that wet supercritical CO2environments lead to significant olivine dissolution, forming Mg-depleted, Si-enriched etched surfaces, and under certain conditions, the formation of passivating silica precipitates. In contrast, reactions in aqueous fluids caused minimal changes in surface chemistry and texture with no silica precipitation. These observations indicate that reaction extent in the CO2-rich phase is greater relative to water-rich mixtures at equivalent temperature, pressure, and reaction duration. The presence of silica precipitates incorporating leached metals indicates limited transport of reactant away from reaction sites in a CO2-rich medium. This study semi-quantitatively evaluates reaction extents in both CO2-rich and aqueous systems across a wide range of parameters, demonstrating faster mineralization in CO2-rich environments and highlighting their potential for enhancing the CO2storage efficiency.

The influence of solvents and salts on the CO2solubility and the impact on esterification reaction kinetics and equilibrium are of particular interest, e.g., for the esterification of acetic acid with ethanol under the influence of CO2, N-methyl-2-pyrrolidone (NMP), or electrolytes. In this work, the equation of state (EOS) electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT advanced) was first applied to predict the CO2solubility in solvent mixtures containing NMP and water with additional electrolytes (NaCl, CsCl). New experimental data on the CO2solubility in electrolyte solutions were measured by two different static synthetic methods, and the ePC-SAFT predictions matched well with the experimental data. As a result, NMP increased the CO2solubility, compared to water as the only solvent, while electrolytes caused a salting-out effect on the CO2solubility in all investigated systems. Further, the kinetics and equilibria of the esterification reaction were studied in the presence of CO2, NMP, and electrolytes. New data were measured by using a high-pressure autoclave with in situATR-FTIR spectroscopy, which enabled real-time monitoring of the kinetic profiles. Therein, CO2and NMP showed a negative effect on the kinetics. However, the additional CO2in the reaction mixture positively influenced the equilibrium, while NMP had a negative influence. Finally, ePC-SAFT advanced was applied to predict the influence of CO2and NMP on both kinetics and equilibrium of ethanol esterification using a thermodynamic activity-based kinetic approach. Therein, the experimental findings were successfully predicted by the model without fitting any model parameter to the experimental data. Ultimately, this approach reduces the experimental effort toward screening most suitable reaction conditions for chemical reactions and screening the influence of other compounds on kinetics and equilibria.

The properties of the interface between materials have practical implications in various fields, encompassing capillary action, foam and emulsion stability, adhesion properties of materials and mass and heat transfer processes. Studying the dynamics of interfaces is also fundamental for understanding intermolecular interactions, change of molecular conformations and molecular aggregations. Pendant-drop tensiometry and its extension, the oscillating drop method, are simple, versatile methods used to measure surface tension, interfacial tension and interfacial rheological properties. These methods can, however, generate unreliable results because of inadequate material preparation, an incorrect calibration method, inappropriate selection of data for analysis, neglect of optical influences or operating the system outside the linear viscoelastic regime. In addition, many studies fail to report accurate uncertainties. This protocol addresses all these critical points and provides detailed descriptions of some operation tips relating to purifying methods for different kinds of material, the time frame for analyzing measurement data, the correction method for optical effects, implementation of the oscillating method with a common programmable pump and remedies for some common problems encountered during the measurement. Examples of interfacial tension measurements for two- and three-phase systems, as well as interfacial dilational modulus measurements for N2and surfactant solutions, are provided to illustrate procedural details and results. A single measurement takes minutes to hours to complete, while the entire protocol, including the leak test, cleaning, repeated measurements and data analysis, may take several days.

The diffusion coefficients of CO2and H2in aqueous solutions are important in numerous processes including carbon capture, geological carbon storage, and reservoir storage of hydrogen. As CO2is reactive in some aqueous solutions, especially aqueous amine solvents for carbon capture, N2O is frequently studied as a surrogate. In this work, the Taylor dispersion technique was used to determine the diffusion coefficients of N2O and H2at high dilution in water at temperatures between 298.15 and 423.15 K and at pressures up to 30 MPa, with a standard relative uncertainty of 1.6%. The new data are intended to resolve significant discrepancies in the literature. The results confirm that temperature is the most important controlling factor and that the diffusion coefficients are nearly independent of pressure in the region studied. The experimental data were correlated using the Stokes–Einstein equation, with average absolute relative deviations of 0.5% for both systems.