Browsing by Author "Castano-Rivera, Patricia"

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    Maximizing Bioethanol Production from Eucalyptus globulus Using Steam Explosion Pretreatment: A Multifactorial Design and Fermenter Development for High Solid Loads
    (2023) Troncoso-Ortega, Eduardo; Valenzuela, Roberto; Reyes-Contreras, Pablo; Castano-Rivera, Patricia; Schiappacasse, L-Nicolas; Parra, Carolina
    Steam explosion pretreatment is suitable for bioethanol production from Eucalyptus globulus wood. Multifactorial experiment designs were used to find the optimal temperature and residence time required to obtain the best glucose yield from the enzymatic hydrolysis of pretreated materials. The chemical composition, crystallinity index, morphology and polymerization degree of the pretreated materials were correlated with enzymatic accessibility. Simultaneous saccharification and fermentation (SSF) using a fed-batch strategy was applied to three different laboratory-scale fermenters. The optimization of the pretreatment was obtained at 208 degrees C and 11 min. However, the enzymatic hydrolysis performance did not show significant differences from the material obtained at 196 degrees C and 9.5 min, which was determined to be the real optimum, owing to its lower energy requirement. The vertical fermenter with type "G" blades and the horizontal fermenter with helical blades were both highly efficient for reaching ethanol yields close to 90% based on dry wood, and ethanol concentrations close to 9.0% v/v.
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    Organic radicals stabilization in natural rubber: Discerning the influence of thermo-oxidation using chemically modified or unmodified lignin as antioxidant
    (2024) Troncoso-Ortega, Eduardo; Castano-Rivera, Patricia; Romero, Romina; Henriquez, Adolfo; Mendez, Camila; Schott, Eduardo; Contreras, David
    We have implemented a lignin compatibilization strategy through silylation and elaborated NR compounds with lignin and silylated lignin. Then, the lignin's contribution to the preservation of physico-mechanical properties and stability of the materials obtained against thermo-oxidation was studied. Thus, our work considered the indirect study of the antioxidant activity on NR compounds by determining the physico-mechanical properties before and after accelerated thermo-oxidative aging, which allowed us to determine that the increase in crosslinking density during the initial hours of accelerated aging was the main observed cause associated with a higher tensile strength retention rate (TSRR: 13.4 %) in NR compound with 5 phr of lignin (CL5) versus a TSRR: 4.7 % for the compound with 5 phr of silylated lignin (CL5Si1). On the other hand, the direct study of the antioxidant capacity by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) using oxygen atmosphere indicated greater thermal stability in NR compounds when lignin is not silylated. The maximum degradation temperature for the CL5 compound was 341.6 degrees C, while for the CL5Si1 compound it was 328.6 degrees C. The oxidation induction temperature (OITtemp) in the CL5 compound was 190.9 degrees C with a peak at 221.0 degrees C, while for CL5Si1 it was 170.3 degrees C with a peak at 194.1 degrees C, indicating again that unsilylated lignin is more suitable as an antioxidant. Finally, through Electron Paramagnetic Resonance (EPR), we determined that the radical quenching effect due to the presence of lignin was significant as the lignin content increases, with a reduction in radical presence close to 50 % compared to a reference compound without lignin.