Examinando por Materia "Silica"
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Ítem Analysis of CO2 adsorption in amine-functionalized porous silicas by molecular simulations(American Chemical Society, 2015-06-01) Builes S.; López-Aranguren, P.; Fraile, J.; Vega, L.F.; Domingo, C.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosWe present the results of a combined experimental-molecular simulations approach concerning the capacity for CO2 adsorption of aminosilica hybrid products synthesized using supercritical fluids. Two porous supports were examined for amine functionalization, an ordered mesoporous silica (MCM-41) and a disordered silica gel (SG40). The textural properties of the studied materials were analyzed by low-temperature N2 adsorption-desorption isotherms and compared to those of molecular simulations using the grand canonical Monte Carlo simulation method. The CO2 adsorption capacity of these materials was evaluated by recording CO2 adsorption isotherms up to 100 kPa. Molecular simulations of the CO2 adsorption behavior of selected samples were performed to gain a fundamental understanding of the effect of functionalization. This study shows that in the functionalized materials, the distance between nitrogen atoms of the grafted amines is a critical factor for the occurrence of CO2 chemisorption, providing some insight into key parameters for designing adsorbent materials for CO2 capture and separation. The relationship between the adsorption results with N2 and CO2 allow us to compare the potential applications of the materials in CO2 adsorption and separation processes. A correlation of the N2 adsorption at a given pressure with the CO2 adsorption at a different pressure allowed the prediction of which materials will perform well for these processes. The hybrid products with high amine density have desirable features required for industrial sorbents, such as an enhanced CO2 adsorption capacity and selectivity. © 2015 American Chemical Society.Ítem Caracterización de la ceniza de hojas de bambú y su influencia como material puzolánico en el concreto(Universidad EAFIT, 2014) Cardona Castro, David Fernando; Acevedo Jaramillo, Ana BeatrizEn este proyecto se pretendió encontrar la metodología para el procesamiento y caracterización química y física de la ceniza de las hojas de bambú -- Para lograr este objetivo se utilizaron diferentes técnicas y procesos -- La ceniza fue producida mediante la calcinación de las hojas de bambú a una temperatura aproximada de 650 °C durante dos horas en un horno eléctrico de laboratorio -- Se evaluó el comportamiento puzolánico entre el hidróxido de calcio Ca(OH)3 y la ceniza obtenida de la hoja de bambú (Blash), utilizando el método de conductividad, basado en la medición de la conductividad eléctrica en una solución Blash / Ca(OH)3 con el tiempo de reacción entre ambos componentes -- Otras técnicas experimentales también fueron empleadas, tales como la fluorescencia de rayos X (FRX), la difracción de rayos X (XRD), microscopía electrónica de barrido (SEM) y la medición de la distribución de tamaño de partícula (DTP) -- Los resultados del análisis químico de la ceniza de las hojas de bambú lograron determinar que este tipo de ceniza está formado por sílice con una naturaleza altamente amorfa y una elevada actividad puzolánica; con la posibilidad de ser usada como material de adición o de reemplazo en la preparación de morteros y concretos de alta resistencia -- La evaluación de sus propiedades físicas o mecánicas se realizó mediante la elaboración de dos mezclas de mortero, la primera denominada mezcla de control y la segunda llamada mezcla de ensayo -- Para esta última se hizo un reemplazo del 20,00% en peso de cemento Portland tipo III por ceniza de hoja de bambú -- Con los cubos de mortero obtenidos se evaluó el índice de actividad de resistencia, por medio del ensayo de compresión simple, fallando cubos a 7 y 28 días -- Del ensayo de resistencia a la compresión se encontró que tanto los cubos de mortero de la mezcla sin reemplazo por ceniza, así como los cubos fallados de la mezcla de ensayo tuvieron resultados de esfuerzo a la compresión muy cercanos -- El índice de actividad puzolánica logrado para la mezcla de ensayo con respecto a la mezcla de control fue de 99,25% para los cubos fallados a los 7 días, y de 95,91% para los cubos fallados a los 28 días -- Para la elaboración de los cubos de mortero con reemplazo de ceniza fue necesario utilizar un 17,77% más de agua que la utilizada en la mezcla de control, alcanzando una relación agua - material cementante (a/cmte) de 0,57; mientras que para la mezcla de control se usó una relación a/cmte de 0,484 -- Si se tiene en cuenta que aumentar la cantidad de agua disminuye la resistencia a la compresión, la gran similitud de los resultados en la resistencia a la compresión de la mezcla de control y la mezcla con reemplazo muestra el excelente comportamiento del reemplazo con cenizas de hoja de bambú -- La ceniza obtenida de las hojas de bambú puede ser considerada como una puzolana natural, de acuerdo con los parámetros de evaluación indicados en la ASTM C618Ítem A Comparative Assessment of Emerging Solvents and Adsorbents for Mitigating CO2 Emissions From the Industrial Sector by Using Molecular Modeling Tools(Frontiers Media S.A., 2020-01-01) Bahamon D.; Alkhatib I.I.I.; Alkhatib N.; Builes S.; Sinnokrot M.; Vega L.F.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosThe possibilities offered by molecular modeling tools to obtain relevant data at process conditions, while also gaining molecular insights on the techniques used for CO2 capture and separation, are presented here using selected case studies. Two different technologies, absorption with amine-based systems and adsorption on porous materials, were explored, using the molecular-based equation of state, soft-Statistical Associating Fluid Theory (SAFT), and Grand Canonical Monte Carlo simulations, respectively. The aqueous monoethanolamine (MEA) system was set as the benchmark for absorption and compared to the performance of 8 alternative amine-based systems, while 16 adsorbents belonging to different families (zeolites, metal–organic frameworks, amorphous silicas, and activated carbons), bare or functionalized with alkylamines, were investigated for the separation of CO2 by adsorption. In addition to obtaining molecular information on the CO2 capture process, the models were further used to examine the CO2 capture performance in terms of cyclic working capacity and energy index as key performance indicators, allowing the identification of promising systems that can improve the current ones to be further evaluated for separation in non-power industries. Results show that for the same total amine mass concentration, non-aqueous amine solvents have a 5–10% reduction in cyclic working capacity, and a 10–30% decrease in the energy index compared to their aqueous counterparts due to their lower heat of vaporization and specific heat capacity. In addition, M-MOF-74, NaX, and NaY structures present the best results for adsorption in temperature swing adsorption (TSA) processes. Similar values of energy requirements to those of amine-based systems (2–2.5 MJ kg CO2–1) were obtained for some of the adsorbent; however, the disadvantage of the TSA process versus absorption should be considered. These results confirm the reliability of molecular modeling as an attractive and valuable screening tool for CO2 capture and separation processes. © Copyright © 2020 Bahamon, Alkhatib, Alkhatib, Builes, Sinnokrot and Vega.Ítem Componentes alternativos para la producción de concreto en la construcción de vivienda ambientalmente sostenible(Universidad EAFIT, 2011) Mejía Martino, Marlon Esteban; Acevedo Jaramillo, Ana BeatrízÍtem EMIR optomechanics(SPIE-INT SOC OPTICAL ENGINEERING, 2004-09-01) Barrera, Sonia; Villegas, Alejandro; Fuentes, Javier; Correa, Santiago; Pérez, Jaime; Redondo, Pablo; R. Restrepo; Sánchez, Vicente; Tenegi, Fabio; Garzón, Francisco; Patrón, Jesus; Universidad EAFIT. Departamento de Ciencias Básicas; Óptica AplicadaEMIR is a NIR multiobject spectrograph with imaging capabilities to be used at the GTC. A general description of instrument performances, as well as the updated optical and mechanical layouts, can be found elsewhere on these proceedings.Ítem Hybrid aminopolymer-silica materials for efficient CO2 adsorption(ROYAL SOC CHEMISTRY, 2015-01-01) López-Aranguren, P.; Builes S.; Fraile, J.; López-Periago, A.; Vega, L.F.; Domingo, C.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosThe present work focuses on the development of a new eco-efficient chemical method for the polymerization of aziridine to hyperbranched polyethyleneimine (PEI) into mesoporous silica by using compressed CO2 as a solvent, reaction medium and catalyst. PEI was in situ grafted into MCM-41 and silica gel substrates, with pore diameters of 3.8 and 9.0 nm, respectively. The optimal polymerization conditions were found by varying the reaction pressure (1.0-10 MPa), temperature (25-45°C) and time (20-400 min). The thermal stability analysis indicated that aminopolymer chains were covalently attached on the amorphous silica surface. The described compressed CO2 route for the synthesis of high amine content hybrid products (6-8 mmolN g-1) is a very fast method, with processing times in the order of few minutes even at very low working pressures (1.0 MPa), being a step forward in the design of efficient hybrid aminopolymer nanocomposites for CO2 capture. The adsorptive behavior of the prepared hybrid materials was experimentally established by recording the N2 (-196°C) and CO2 (25, 50 and 75°C) adsorption isotherms. Results were compared to molecular simulation studies performed using Grand Canonical Monte Carlo for either N2 or CO2 adsorbed on amino modified MCM-41, thus helping to elucidate the predominant PEI configuration present in the functionalized materials. © The Royal Society of Chemistry 2015.Ítem Propuesta paleoambiental para el Cretácico Tardío en el noreste de la Cuenca del Valle Medio del Magdalena(Universidad EAFIT, 2023) Múnera Montoya, Lizeth Katherine; Juliao Lemus, Tatiana Milena; Marsifi, Nelbett; Caballero, Víctor ManuelÍtem Sectorización de arenas silíceas por bloques para el avance de los frentes de explotación: Titulo minero 2406 - Compañía PELDAR S.A.(Universidad EAFIT, 2016) Álvarez Ramírez, Daniel; Marín Cerón, María Isabel; Gómez Ramírez, Carlos JaimeÍtem Superhydrophobic bilayer coating based on annealed electrospun ultrathin poly("-caprolactone) fibers and electrosprayed nanostructured silica microparticles for easy emptying packaging applications(MDPI AG, 2018-05-01) Lasprilla-Botero, J.; Torres-Giner, S.; Pardo-Figuerez, M.; álvarez-Láinez, M.; Lagaron, J.M.; Universidad EAFIT. Departamento de Ingeniería de Diseño; Ingeniería de Diseño (GRID)A coating rendering superhydrophobic properties to low-density polyethylene (LDPE) films used in packaging applications was herein generated by means of the electrohydrodynamic processing (EHDP) technique. To this end, electrospun ultrathin poly("-caprolactone) (PCL) fibers, followed by electrosprayed nanostructured silica (SiO2) microparticles, were deposited on top of the LDPE film. Various electrospinning and electrospraying times were tested and optimized followed by a thermal post-treatment to provide physical adhesion between the bilayer coating and the LDPE substrate. The morphology, hydrophobicity, permeance to limonene, and thermal stability of the resultant nanostructured coatings were characterized. It was observed that by controlling both the deposition time of the electrospun ultrathin PCL fibers and the electrosprayed SiO2 microparticles, as well as the conditions of the thermal post-treatment, effective superhydrophobic coatings were developed onto the LDPE films. The resultant multilayer presented a hierarchical micro/nanostructured surface with an apparent contact angle of 157° and a sliding angle of 8°. The addition of silica reduced, to some extent, the limonene (aroma) barrier, likely due to the increased surface-to-volume ratio, which allowed permeant sorption to occur but improved the thermal stability of the LDPE/PCL film. As a result, the developed multilayer system of LDPE/PCL/SiO2 has significant potential for use in easy-to-empty packaging applications of high water activity products. © 2018 by the authors.