Browsing by Author "Olivares, Douglas"

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    Long-Term Evaluation of a Ternary Mixture of Molten Salts in Solar Thermal Storage Systems: Impact on Thermophysical Properties and Corrosion
    (2024) Henriquez, Mauro; Reinoso-Burrows, Juan Carlos; Pasten, Raul; Soto, Carlos; Duran, Carlos; Olivares, Douglas; Guerreiro, Luis; Cardemil, Jose Miguel; Madrid, Felipe M. Galleguillos; Fuentealba, Edward
    Solar thermal plants typically undergo trough operational cycles spanning between 20 and 25 years, highlighting the critical need for accurate assessments of long-term component evolution. Among these components, the heat storage media (molten salt) is crucial in plant design, as it significantly influences both the thermophysical properties of the working fluid and the corrosion of the steel components in thermal storage systems. Our research focused on evaluating the long-term effects of operating a low-melting-point ternary mixture consisting of 30 wt% LiNO3, 57 wt% KNO3, and 13 wt% NaNO3. The ternary mixture exhibited a melting point of 129 degrees C and thermal stability above 550 degrees C. Over 15,000 h, the heat capacity decreased from 1.794 to 1.409 J/g degrees C. Additionally, saline components such as CaCO3 and MgCO3, as well as lithium oxides (LiO and LiO2), were detected due to the separation of the ternary mixture. A 30,000 h exposure resulted in the formation of Fe2O3 and the presence of Cl, indicating prolonged interaction with the marine environment. This investigation highlights the necessity of analyzing properties under actual operating conditions to accurately predict the lifespan and select the appropriate materials for molten salt-based thermal storage systems.
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    Sulfate-modified MOF-808 as a superacid catalyst: a performance evaluation of Zr(iv) and Hf(iv) analogues in acetalization reactions
    (2025) Roa Gómez, Vanesa Belen; Cea, Sebastián; Pazo Carballo, César Alexander; Llanos, Jaime; Olivares, Douglas; Escalona, Néstor; Leiva Campusano, Ángel; Hidalgo-Rosa, Yoan; Zarate, Ximena; Dongil, Ana Belén; Schott Verdugo, Eduardo
    In this study, we report the synthesis and characterization of MOF-808-SO4-M (M = Zr(IV), Hf(IV)), derived from MOF-808-M precursors. The introduction of sulfate groups enhances the Brønsted acidity of these materials, significantly improving their catalytic performance in the benzaldehyde acetalization reaction. The materials were characterized using powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), nitrogen adsorption–desorption analysis, thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS), and Hammett indicator tests. Catalytic evaluation revealed that MOF-808-SO4-Zr exhibited significantly higher conversion compared to its Hf-based analogue, a difference attributed to its greater density of acid sites, as confirmed by temperature-programmed surface reaction (TPSR) analysis. These experimental results were further supported by density functional theory (DFT) calculations, which provided insights into the acidic properties and catalytic behavior of the materials.