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Acceso Abierto A novel one-dimensional model to predict fin efficiency of continuous fin-tube heat exchangers(2019) Suárez, Felipe; Keegan, Sergio D.; Mariani, Néstor Javier; Barreto, Guillermo FernandoThe objective of this contribution is to present a novel one-dimensional (1D) model to predict the heat transfer rate from (or to) continuous fin-and-tube heat exchangers. In this model, called two equivalent radial fins (1D-TERF), it is proposed to represent the thermal behavior of the continuous two dimensional (2D) fin by employing two thermally independent sections of radial fins, while keeping the total surface area of the actual fin and the outer perimeter of the tube. The two geometrical free parameters of the model are obtained by matching the two first terms of the series describing the actual fin efficiency at low values of the modulus, . It is demonstrated that the 1D-TERF model with this criterion allows estimating the fin efficiency with a higher level of precision than any other literature alternative (as the radial equivalent fin model and the sector method) over a wide range of conditions (i.e., values of between 0 and infinity) for circular tubes with in-line and staggered layouts in an extensive range of geometric ratios. - Documento de conferencia
Acceso Abierto Producción de bioaditivos y biosurfactantes con aplicación en la industria de los combustibles(2020) Casella, Mónica LauraEl interés de este proyecto es generar aditivos oxigenados a base de glicerol y furfural, los cuales son biodegradables, no tóxicos y renovables. Los aditivos para combustibles son sustancias que se agregan o mezclan con combustibles, especialmente gasolina, diesel o biodiesel, para mejorar sus propiedades combustibles y lograr un mejor rendimiento. El agotamiento de los combustibles fósiles ha intensificado la investigación y la utilización de combustibles renovables, entre ellos el biodiesel. En el proceso de producción de biodiesel, por cada 100 kg de biodiesel producido, se generan 10 kg de glicerol. En vista de las características y potenciales del glicerol, se están incrementando los esfuerzos para convertirlo en productos de mayor valor, lo que a su vez mejorará la economía general de la producción de biodiesel. Por otra parte, la renovabilidad y abundancia de biomasa lignocelulósica la convierten en un recurso viable para la producción de plataformas químicas como el furfural. Actualmente, el furfural se produce industrialmente mediante la hidrólisis ácida de biomasa de origen agrícola. Se propone el acoplamiento de furfural con glicerol para producir el 1,3-dioxolano en condiciones catalíticas y sin solventes. Los 1,3-dioxolanos pueden ser utilizados como aditivos de combustible. - Artículo
Acceso Abierto Ultrasound Assisted Electrodeposition of Cu-SiO2 Composite Coatings: Effect of Particle Surface Chemistry(2019) Bengoa, Leandro N.; Ispas, A.; Bengoa, José Fernando; Bund, A.; Egli, Walter AlfredoElectrodeposition of Cu-SiO2 composite coatings from an alkaline non-cyanide electrolyte containing glutamate as complexing agent was studied. Silica mesoporous particles were synthesized using a modified Stöber methodology, and later their surface chemistry was changed by functionalizing them with 3-aminopropyltriethoxysilane. Particles microstructure and morphology were characterized (SEM, TEM, XRD) and their charging behavior in several electrolytes was studied through ζ -potential measurements. Galvanostatic deposition was performed in electrolytes containing both as-prepared and functionalized SiO2 at various current densities, and the influence of ultrasonic irradiation (37 Hz) was evaluated. For some experiments, 1.5 g L− of Polyquaternium 7 were added to the solution. SEM and XRD were used to characterized coatings morphology and microstructure, whereas EDS was used to estimate SiO2 wt%. The results showed that the effect of ultrasound on the codeposition process depends on current density and particle surface chemistry. All the trends observed in this study could be explained taking into account ζ -potential values recorded and previously reported theories. Adjusting the experimental conditions, it was possible to obtain deposits with SiO2 contents of ≈5 wt%. Finally, it was found that both ultrasonic irradiation and Polyquaternium 7 affect the morphology and crystal orientation of the deposits. - Artículo
Acceso Abierto Preparation and characterization of a supported system of Ni2P/Ni12P5 nanoparticles and their use as the active phase in chemoselective hydrogenation of acetophenone(2018) Costa, Dolly Carolina; Soldati, Analía L.; Pecchi, Gina; Bengoa, José Fernando; Marchetti, Sergio Gustavo; Vetere, VirginiaNi2P/Ni12P5 nanoparticles were obtained by thermal decomposition of nickel organometallic salt at low temperature. The use of different characterization techniques allowed us to determine that this process produced a mixture of two nickel phosphide phases: Ni2P and Ni12P5. These nickel phosphides nanoparticles, supported on mesoporous silica, showed activity and high selectivity for producing the hydrogenation of the acetophenone carbonyl group to obtain 1-phenylethanol. This is a first report that demonstrates the ability of supported Ni2P/Ni12P5 nanoparticles to produce the chemoselective hydrogenation of acetophenone. We attribute these special catalytic properties to the particular geometry of the Ni–P sites on the surface of the nanoparticles. This is an interesting result because the nickel phosphides have a wide composition range (from Ni3P to NiP3), with different crystallographic structures, therefore we think that different phases could be active and selective to hydrogenate many important molecules with more than one functional group. - Artículo
Acceso Abierto Phosphorus as a promoter of a nickel catalyst to obtain 1-phenylethanol from chemoselective hydrogenation of acetophenone(2019) Costa, Dolly Carolina; Soldati, Analía Leticia; Bengoa, José Fernando; Marchetti, Sergio Gustavo; Vetere, VicenteTwo catalysts were prepared using monodisperse pre-synthetized nanoparticles of metallic nickel and nickel phosphides with the same average diameter. Both nanoparticles species were deposited on the same support: mesoporous silica nano-spheres of MCM-41. This support is suitable to inhibit agglomeration and sintering processes during preparation steps. Therefore, two supported and activated catalysts with the same average nanoparticles diameter were obtained. They differ only in the nature of the active species: metallic nickel and nickel phosphides. The effect of the presence of a second element (phosphorus), more electronegative than nickel, on the activity and selectivity in the chemoselective hydrogenation of acetophenone was studied. The reaction conditions were: H2 pressure of 1 MPa, 80°C using n-heptane as solvent. With the aim to understand the catalytic results, nanoparticles, support and catalysts were carefully characterized by X-ray diffraction, diffuse light scattering, transmission electron microcopy, high resolution transmission electron microcopy, selected area electron diffraction, scanning electron microcopy, Fourier transformer infrared spectroscopy, N2 adsorption at -196 °C, atomic absorption, H2 and CO chemisorption and volumetric oxidation. Considering these results and geometric and electronic characteristics of the surface of both active species, a change in the adsorption intermediate state of acetophenone in presence of phosphorus is proposed to explain the hydrogenation chemoselectivity of nickel phospides - Artículo
Acceso Abierto Zirconia-Supported Silver Nanoparticles for the Catalytic Combustion of Pollutants Originating from Mobile Sources(2019) Montaña, Maia; Leguizamón Aparicio, María Silvia del Valle; Ocsachoque, Marco; Navas, Marisa B.; Barros, Ivoneide de C. L.; Rodríguez-Castellón, Enrique; Casella, Mónica Laura; Lick, Ileana D.This work presents the physicochemical characterization and activity of zirconia-supported silver catalysts for the oxidation of pollutants present in diesel engine exhaust (propane, propene, naphthalene and soot). A series of silver-supported catalysts AgxZ (x = 1, 5 and 10 wt.%, Z = zirconia) were prepared, which were studied by various characterization techniques. The results show that silver is mainly found under the form of small metal nanoparticles (<10 nm) dispersed over the support. The metallic phase coexists with the AgOx oxidic phases. Silver is introduced onto the zirconia, generating Ag–ZrO2 catalysts with high activity for the oxidation of propene and naphthalene. These catalysts also show some activity for soot combustion. Silver species can contribute with zirconia in the catalytic redox cycle, through a synergistic effect, providing sites that facilitate the migration and availability of oxygen, which is favored by the presence of structural defects. This is a novel application of the AgOx–Ag/ZrO2 system in the combustion reaction of propene and naphthalene. The results are highly promising, given that the T50 values found for both model molecules are quite low. - Artículo
Acceso Abierto Backscattered electron images, X-ray maps and Monte Carlo simulations applied to the study of plagioclase composition in volcanic rocks(2013) Galván Josa, V.; Fracchia, D.; Castellano, G.; Crespo, E.; Kang, Kyun Won; Bonetto, RitaZoning patterns in plagioclases are related to abrupt changes in the anorthite content along the crystal growing direction. Accurate characterization of these patterns by electron microprobe is useful to identify magma chamber processes such as recharge, mingling and whole-chamber overturn events. In this work, a new procedure to obtain high resolution quantitative maps of anorthite concentration in single plagioclase crystals is developed. The methodology consists in performing a calibration of backscattered electron images using quantitative X-ray maps. The ultimate resolution of charac- teristic X-rays and backscattered electron signals is studied by Monte Carlo simulation. The method is applied to characterize the chemical composition of a volcanic plagioclase from the Cerro Vilama, Argentina. The results obtained are more precise than the values given by the methods commonly used in the study of plagioclase composition, i.e. the classical profiling by electron microprobe point analysis or the modern backscattered electron image calibration by means of quantitative energy or wavelength dispersive X-ray analysis at a few selected points. - Artículo
Acceso Abierto Uncertainty studies of topographical measurements on steel surface corrosion by 3D scanning electron microscopy(2012) Kang, Kyun Won; Pereda, María Dolores; Canafoglia, María Elena; Bilmes, Pablo David; Llorente, Carlos Luis; Bonetto, RitaPitting corrosion is a damage mechanism quite serious and dangerous in both carbon steel boiler tubes for power plants which are vital to most industries and stainless steels for orthopedic human implants whose demand, due to the increase of life expectation and rate of traffic accidents, has sharply increased. Reliable methods to characterize this kind of damage are becoming increasingly necessary, when trying to evaluate the advance of damage and to establish the best procedures for component inspection in order to determine remaining lives and failure mitigation. A study about the uncertainties on the topographies of corrosion pits from 3D SEM images, obtained at low magnifications (where errors are greater) and different stage tilt angles was carried out by using an in-house software previously developed. Additionally, measurements of pit depths on biomaterial surfaces, subjected to two different surface treatments on stainless steels, were carried out. The different depth distributions observed were in agreement with electrochemical measurements. - Documento de conferencia
Acceso Abierto Presentación institucional del CINDECA: desarrollo de la línea de investigación en valorización catalítica de biomasa(2018) Casella, Mónica LauraEl CINDECA fue incorporado como Centro de triple dependencia CONICET-UNLP-CIC en diciembre de 2017. En este primer encuentro como Centro CIC, se hará una breve descripción de la composición de su planta de personal, su infraestructura y de las líneas de trabajo que se desarrollan en el instituto. De entre las líneas de investigación, se hará una presentación del grado de avance del Proyecto de Innovación y Transferencia en Áreas Prioritarias de la provincia de Buenos Aires (PIT-APBA) “Generación de energías renovables y valorización de biomasa residual de la región Noroeste de la provincia de Buenos Aires mediante procesos catalíticos sustentables”. - Resumen
Acceso Abierto Nuevos materiales magnéticos basados en heteropoliácidos tipo Keggin y su aplicación en reacciones de esterificación del ácido levulínico para valorización de residuos de biomasa(2018) Escobar Caicedo, Angélica M.; Blanco, Mirta Noemí; Martínez Zambrano, José J.; Cubillos Lobo, Jairo A.; Pizzio, Luis René; Romanelli, GustavoEste trabajo se encuentra dirigido a valorizar residuos de biomasa, mediante catálisis heterogénea a través del estudio de un nuevos material sólido basado en ácido tungstofosfórico (TPA), un heteropoliácido tipo Keggin, inmovilizado sobre materiales magnéticos recubiertos con sílice mesoporosa sintetizados vía sol-gel, y su aplicación en reacciones de esterificación para la obtención de compuestos de alto valor agregado derivados de biomasa. La actividad catalítica se estudió en la síntesis de levulinato de n-butilo a partir de ácido levulínico y nbutanol, producto de gran importancia por sus usos, como fragancia o como aditivo en gasolina y biodiesel, entre otros. - Resumen
Acceso Abierto Síntesis multicomponente de dihidropirimidonas derivadas de furfurales catalizada por H₁₄NaP₅W₂₉MoO₁₁₀@SiO₂(2018) Portilla Zúñiga, Omar M.; Romanelli, Gustavo; Sathicq, Ángel G.El furfural (2-furfuraldehído) es universalmente obtenido a partir de la biomasa representando una forma estándar de aprovechar y dar valor añadido a residuos agrícolas y forestales. El proceso es simple; de estos residuos se obtienen pentosanos que, mediante hidrólisis ácida y la posterior ciclo-deshidratación de los monosacáridos formados termina por generar el aldehído. A partir del furfural se pueden obtener una gran variedad de compuestos de interés industrial y también puede ser usado como material de partida para la síntesis de dihidropirimidinonas. Las 2-oxo- y tioxo-1,2,3,4-tetrahidropirimidinas (3,4-dihidropirimidina- 2(1H)-tionas) son compuestos atractivos ya que tienen una amplia gama de actividades biológicas; antibacteriales, antiinflamatorias, antivirales y como moduladores de los canales de calcio. - Artículo
Embargado One-pot synthesis of ferrocenyl-pyrimidones using a recyclable molibdosilicic H4SiMo12O40 heteropolyacid(Springer International Publishing, 2016) Jios, Jorge; Metzler-Nolte, Nils; Vázquez, Patricia Graciela; Romanelli, GustavoA series of ferrocene-containing dihydropyrimidines (DHPs) were prepared by the one-pot Biginelli reaction of formylferrocene, 1,3-dicarbonyl component and urea/thiourea. The reaction was catalyzed by a commercial Keggin heteropolyacid (H4SiMo12O40) as a safe, clean and recyclable catalyst. Three different synthetic protocols were examined in order to improve the yields of the reaction and to elucidate its mechanism. Intermediates of the competitive Knoevenagel reaction were also isolated. The methodology is operationally simple and provides access to highly substituted dihydropyrimidines containing ferrocene in very good yields. The catalyst can be used and recycled without appreciable loss of the catalytic activity. - Artículo
Embargado Carbon-supported metal-modified lacunary tungstosilicic polyoxometallates used as catalysts in the selective oxidation of sulfides(2015) Frenzel, Romina; Sathicq, Ángel G.; Blanco, Mirta Noemí; Romanelli, Gustavo; Pizzio, Luis RenéLacunary tungstosilicic polyoxometallates modified with transition metal ions [SiW11O39M(H2O)]6−, where M=Mn2+, Fe2+, Co2+or Cu2+, were synthesized and supported on activated carbon to obtain the SiW11MC catalysts. The samples were characterized by FT-IR, XRD, N2 adsorption–desorption measurements, and the acidic properties were determined using the isopropanol dehydration test reaction. The activity and selectivity of the catalysts were evaluated in the selective oxidation of a series of sulfides to sulfoxides or sulfone. The reaction was carried out in acetonitrile as solvent using H2O2 35% p/V as a clean oxidant. The conversion values decreased in the following order: SiW11MnC> SiW11FeC > SiW11CuC > SiW11CoC. The catalysts were reused without appreciable loss of their catalytic activity. It was found that the activity of the catalysts decreases in parallel with the increment in the reduction temperature values. The most easily reducible catalyst displayed the highest conversion values. We found a convenient and selective procedure for oxidizing sulfides to sulfoxides or sulfones using aqueous hydrogen peroxide and a catalytic amount of lacunary tungstosilicic polyoxometallates supported on carbon at low temperatures (20–50 ◦C) in a reasonably short reaction time. - Comunicacion
Acceso Abierto Transferencia de calor en reactores trickle-bed: influencia de la forma y tamaño del relleno(2015) Taulamet, María José; Mariani, Néstor Javier; Martínez, Osvaldo Miguel; Barreto, Guillermo FernandoSe realizaron medidas de transferencia de calor con un equipo experimental del tipo trickle bed. A partir de la mediciones experimentales realizadas de los perfiles radiales de temperatura para distintos tipos de relleno (esferas, cilindros, trilobulares), cubriendo como principales variables operativas los caudales de líquido y gas, altura de relleno y relación de aspecto (se cubrió un rango de 4 a 35, típico de sistemas con transferencia de calor con el exterior), se aplicará el modelo bidimensional pseudohomogéneo para interpretar el fenómeno de transferencia de calor. Los parámetros correspondientes al modelo serán ajustados por regresión de la información experimental, para generar finalmente correlaciones con fines predictivos. - Artículo
Acceso Abierto Dynamic laser speckle technique as an alternative tool to determine hygroscopic capacity and specific surface area of microporous zeolites(2018) Mojica Sepúlveda, Ruth Dary; Mendoza Herrera, Luis Joaquín; Grumel, Eduardo Emilio; Soria, Delia Beatriz; Cabello, Carmen Inés; Trivi, Marcelo RicardoAdsorption phenomena have several technological applications such as desiccants, catalysts, sep- aration of gases, etc. Their uses depend on the textural properties of the solid adsorbent and the type of the adsorbed liquid or gas. Therefore, it is important to determine these properties. The most common measurement methods are physicochemical based on adsorption of N2 to determine the surface area and the distribution of pores size. However these techniques present certain limi- tations for microporous materials. In this paper we propose the use of the Dynamic Laser Speckle (DLS) technique to measure the hygroscopic capacity of a microporous natural zeolite and their modi ed forms. This new approach based on the adsorption of water by solids allows determine their speci c surface area (S). To test the DLS results, we compared the obtained S values to those calculated by di erent conventional isotherms using the N2 adsorption-desorption method. - Artículo
Acceso Abierto Hydro-Adsorption Study by Dynamic Laser Speckle of Natural Zeolite for Adsorbent and Fertilizer Applications(2016) Mojica Sepúlveda, Ruth Dary; Mendoza Herrera, Luis Joaquín; Agosto, María Florencia; Grumel, Eduardo Emilio; Soria, Delia Beatriz; Cabello, Carmen Inés; Trivi, Marcelo RicardoThe dynamic behavior caused by hydro-adsorption process of materials based on a rich mineral clinoptilolite together with their acidic, basic and calcinated forms has been studied by the dynamic laser speckle (DLS) technique. We propose a modified Peleg’s equation to improve fitting of DLS data. Textural (BET), structural (XRD) and spectroscopic (FTIR) properties were also studied and compared. We demonstrated that DLS was the most sensitive, simple and inexpensive method for comparing the performance of adsorptive materials with slightly modified surfaces. It also allowed the correlation with physicochemical properties. - Documento de conferencia
Acceso Abierto Una revisión crítica de la transferencia de calor en sistemas trickle-bed(2013) Mariani, Néstor Javier; Barreto, Guillermo Fernando; Martínez, Osvaldo M.; Taulamet, María JoséEn diversos sistemas en los cuales se emplean reactores de lecho fijo con flujo bifásico descendente (trickle-bed) la transferencia de calor cumple un rol significativo en el comportamiento del reactor. La información bibliográfica para predecir la capacidad de transferencia de calor es errática. En este trabajo se ha llevado a cabo una revisión crítica sobre el conocimiento del tema. Se han analizado métodos experimentales para la obtención de datos, modelos empleados para la interpretación de los mismos y correlaciones propuestas. Se determinaron inconsistencias en numerosas correlaciones, falencias en el conocimiento, tanto de información experimental como de correlaciones, y se propusieron nuevas correlaciones para la conductividad térmica efectiva radial del lecho. - Artículo
Acceso Abierto Total Oxidation of Naphthalene with Zirconia-Supported Cobalt, Copper and Nickel Catalysts(MDPI (Multidisciplinary Digital Publishing Institute), 2017) Leguizamón Aparicio, María Silvia del Valle; Ocsachoque, Marco; Gazzoli, Delia; Botto, Irma; Lick, IleanaZrO2 nH2O (hydrogel) impregnated with transition metals (Cu, Co, and Ni) was studied in this work as a precursor for the synthesis of CuO/ZrO2 (CuZ), CoOx/ZrO2 (CoZ), and NiO/ZrO2 (NiZ) catalysts, employed in the naphthalene oxidation reaction. Fresh and catalytically used materials were characterized by different physicochemical techniques, to compare the bulk and surface behavior, with particular attention to the effect of the supported metal species’ properties on the catalytic activity. Techniques such as X-ray diffraction (XRD), temperature programmed reduction (TPR), differential scanning calorimetry (DSC), Brunauer–Emmett–Teller (BET) surface area analyzer, diffuse reflectance spectroscopy (DRS UV–vis), and Raman spectroscopy, allow for establishing structural and textural aspects of the support, as well as the surface coordination and the accessibility of supported species. Results were in agreement with the CuZ > CoZ > NiZ sequence for the activity in naphthalene oxidation reaction. Electronic properties, ionic sizes, oxide phase deposition on the support surface, reducibility, metal–support interaction, and local site symmetry of metals seem to be decisive factors for the catalytic interaction with the gaseous phase. - Artículo
Acceso Abierto Hydrothermal Stability of Ru/SiO2–C: A Promising Catalyst for Biomass Processing through Liquid-Phase Reactions(MDPI (Multidisciplinary Digital Publishing Institute), 2017) Gatti, Martín N.; Lombardi, María Bárbara; Gazzoli, Delia; Santori, Gerardo Fabián; Pompeo, Francisco; Nichio, Nora N.In this work, structural and morphological properties of SiO2–C composite material to be used as support for catalysts in the conversion of biomass-derived oxygenated hydrocarbons, such as glycerol, were investigated in liquid water under various temperatures conditions. The results show that this material does not lose surface area, and the hot liquid water does not generate changes in the structure. Neither change in relative concentrations of oxygen functional groups nor in Si/C ratio due to hydrothermal treatment was revealed by X-ray photoelectron spectroscopy (XPS) analysis. Raman analysis showed that the material is made of a disordered graphitic structure in an amorphous silica matrix, which remains stable after hydrothermal treatment. Results of the hydrogenolysis of glycerol using a Ru/SiO2–C catalyst indicate that the support gives more stability to the active phase than a Ru/SiO2 consisting of commercial silica. - Artículo
Acceso Abierto Efficient deprotection of phenol methoxymethyl ethers using a solid acid catalyst with Wells-Dawson structure(MDPI (Multidisciplinary Digital Publishing Institute), 2001) Romanelli, Gustavo; Autino, Juan Carlos; Baronetti, Graciela T.; Thomas, HoracioDeprotection of various phenols from their respective methoxymethyl ethers using an heteropolyacid catalyst was studied. The catalyst was the Wells-Dawson heteropolyacid, used both in bulk or supported on silica. Yields were high to quantitative after less than one hour reaction time and the catalyst was easily recoverable and reusable.