Artículos, informes y presentaciones en Congresos



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  • Artículo
    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 Fernando
    The 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 Laura
    El 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 Alfredo
    Electrodeposition 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, Virginia
    Ni2P/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, Vicente
    Two 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