Browsing by Author "Area, María Cristina"

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    Hydroxymethylation of technical lignins from south-american sources with potential use in phenolic resins.
    (2019-02-16) Taverna, María E.; Estenoz, Diana; Nicolau, Verónica V.; Felissia, Fernando; Area, María Cristina
    This work investigates the valorization of sodium lignosulfonate, kraft, and organosolv lignins from South America. A detailed characterization of the lignins and their chemical modification by hydroxymethylation, a reaction between lignin and formaldehyde, were performed. The characterization included measurements of moisture, ash, and carbohydrate contents, elemental and thermogravimetric analysis (TGA), and functional groups and molar mass distributions by Fourier transform infrared spectroscopy (FTIR) and size exclusion chromatography (SEC), respectively. Also, reactive aromatic hydrogens (—HAr) were quantified by the measurement of phenolic hydroxyl groups (P-OH) content by UV-Vis spectroscopy. The different initial formaldehyde/lignin weight ratios (0.07, 1.47), temperatures (40 ºC, 50 ºC, 70 ºC) and pHs (9, 11); and the following of hydroxymethylation reactions by UV-Vis spectroscopy were investigated. All lignins resulted attractive for the use as replacement of phenol in phenolic resins but sodium lignosulfonate was the most appropriate due to its water solubility.
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    Improvement of bioethanol production from rice husks
    (2020-07) Arismendy Pabón, Ana María; Felissia, Fernando Esteban; Mendieta, Carolina Mónica; Chamorro, Ester Ramona; Area, María Cristina
    This work aimed to compare the production of bioethanol from rice husk through simultaneous hydrolysis and fermentation process (SSF) with that through hydrolysis followed by fermentation process (SHF). The raw material was pretreated under mild conditions with sodium hydroxide. Initially, the influence of particle size was evaluated in the enzymatic hydrolysis of pretreated milled and unmilled husk. Subsequently, the efficiencies of Saccharomyces cerevisiae IMR 1181 (SC 1181) and Saccharomyces cerevisiae IMR 1507 (SC 1507) yeasts were compared using the SSF process. Finally, the SSF and SHF processes were compared using the SC 1181 yeast. Although a little more glucose was generated using ground husk (36.6% vs. 35.5%), grinding costs have to be also considered. The SC1507 yeast performed best at all times. The bioethanol yields for SHF and SSF with SC 1181 were of 35.3% and 38.2%, respectively. Maximum yields in SSF were of 43.9% for SC 1507 and 38%for SC 1181.
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    Optimización de la hidrolisis enzimática de la cascarilla de arroz
    (2019-11-04) Arismendy, Ana María; Villa Retrepo, Andrés Felipe; Alcaraz, Wilman; Chamorro, Ester; Area, María Cristina
    El objetivo de este trabajo fue encontrar las condiciones óptimas de hidrólisis enzimática de la cascarilla de arroz pretratada con hidróxido de sodio en autoclave a 121° C. Se evaluaron las variables: FPU/ g sustrato, pH, agitación, tiempo, temperatura y concentración de surfactante mediante un diseño de cribado, resultando estadísticamente significativas todas las variables. Seguidamente se aplicó un diseño de optimización para las variables: pH, FPU y tiempo, descartando las de menor nivel de significación. Finalmente, las mejores condiciones encontradas en los diseños anteriores fueron (pH 5.0, 13 h, y 30 FPU / g de sustrato) posteriormente se aplicaron estas condiciones en experiencias para evaluar la influencia del aumento de celulosa hidrolizable, usando 6%; 8% y 10% de celulosa disponible con rendimientos de sacarificación de 74%, 42% y 16%.
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    Optimization of the soda-ethanol delignification stage for a rice husk biorefinery
    (2017-03-01) Dagnino, Eliana Paola; Felissia, Fernando E.; Chamorro, Ester Ramona; Area, María Cristina
    The aim of this work was to optimize the delignification of the hemicelluloses-free fraction of rice husk to obtain fractions of lignin, cellulose, and inorganics, which could be valorized in the context of the rice husk biorefinery. The hemicelluloses were pre-extracted from the raw material by dilute sulfuric acid, and a soda-ethanol-water process was used for delignification. Two experimental designs were carried out to evaluate different ranges of the same variables (strong and light conditions), aiming to promote maximal delignification or delignify while protecting carbohydrates. The optimal delignification points were obtained using 13 and 8% of NaOH (%w/w on solid material), in a 50:50 and 54:46 ethanol:water solution. In these conditions, 94.3 and 90.1% of lignin and almost 100 and 40% of inorganics were removed from the solid, respectively. The used soda-ethanol-water process can be defined as a soda process additivated with ethanol, showing significant advantages over soda-anthraquinone process for the fractionation of lignocellulosic materials.
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    Studies on lignin extraction from rice husk by a soda-ethanol treatment : kinetics, separation, and characterization of products
    (2018-01-01) Dagnino, Eliana Paola; Chamorro, Ester Ramona; Felissia, Fernando E.; Area, María Cristina
    The delignification kinetics of lignocellulosic waste is an important tool for the study of the technical-economic viability of biorefinery processes. The aim of this work was to study the kinetic of lignin extraction by a soda-ethanol treatment of hemicelluloses-free rice husk, within the framework of a biorefinery. Additionally, the type of phenolic structures in the extracted lignin and the behavior of inorganics were evaluated. The kinetic study was carried out at 140, 150, and 160 °C, at different times between 3 and 100 min of reaction for each temperature. A first order kinetic model was adjusted to the experimental data of residual lignin in the treated solid in the fast and slow phase. The kinetic constant k0 varied from 0.021 to 0.035 min−1 for 140–160 °C. The activation energies were 38.59 kJ/mol and 33.47 kJ/mol for the fast and slow phase, respectively. The inorganics components remained in the solid and the proportion of silicon increased through all treatments. About 50% of the initial lignin with 1% of inorganics was recovered by precipitation. The percentage of total OH in lignin remained high, about 8.5%, and decreased with the temperature but not with the time of the reaction.