Browsing by Author "Martínez , María Laura"

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    Aniline adsorption and polymerization over gallium modified mesoporous material.
    (Univesidsad Tecnológica Nacional., 2018) Martínez , María Laura; Rivoira , Lorena Paola; Beltramone, Andrea Raquel; Anunziata, Oscar Alfredo; Anunziata, Oscar Alfredo; Rivoira , Lorena Paola
    In this work we study aniline polymerization over a mesoporous Ga-SBA-3 synthesized in our laboratory. In order to modify the intrinsic acidity of the mesoporous material gallium was incorporated into the structure by post synthesis wet impregnation method using gallium nitrate. Structural and textural characterization of the materials was performed by X-ray diffraction (XRD), ICP and EDX analysis, N2 adsorption-desorption and BET area analysis, FTIR and scanning electron microscopy (SEM). The catalytic material presented a ratio Si/Ga=32. Aniline is a weak organic base and an amphiprotic compound, so it can accept or donate protons. The polyaniline (PANI) exists in diverse ways presenting different chemical and physical properties. The protonated polyaniline feature the conductivity of a semiconductor material, over 100 S/cm. Toward achieve aniline adsorption, the solid gallium silicate was exposed to aniline vapours. The aniline adsorption was studied by infrared spectroscopy and the results obtained were evaluated so as to been able to polymerize it over the mesoporous material generating a unique polyaniline-host composite with new properties. Those polyaniline/hosts composites obtained by a polymerization in-situ technique were characterized by infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. Comparing to previous results FTIR analysis of the polyaniline/Ga SBA-3 composite (PANI/Ga-SBA-3) showed characteristics bands attributed to the quinoidal stretching (N=Q=N) and C-C stretching of the benzene ring. The low angle XRD analysis showed that the mesoporous structure was maintained in spite of the gallium incorporation. The absence of PANI peaks and G2O3 in the wide angle XRD pattern confirms that the polyaniline is adsorbed over the gallium silicate mesoporous surface and the gallium is well dispersed over the support.
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    Preparation of carbon nanotubes with hybrids nanostructure materials.
    (Univesidsad Tecnológica Nacional., 2017) Martínez , María Laura; Juárez , Juliana María; Gómez Costa, Marcos Bruno; Beltramone, Andrea Raquel; Juárez , Juliana María
    Carbon nanotubes (CNT's) are allotropes carbon, like diamond, graphite and fullerenes. There are different types of CNT's, depending on the type of the graphite layers, it can be single wall carbon nanotubes (SWCNT's) and multi wall carbon nanotubes (MWCNT's). These nanomaterials show good physical properties such as their density, strength and thermal conductivity. The controllable synthesis of materials with the desired structure and dimensionality is of great significance in material science. In this work, the hierarchical carbon nanotubes (CNTs) were synthesized via a simple chemical conversion route by using Carbon Substrate/Fe3O4-SBA-15 hybrid (all in one). The synthesis of Carbon Substrate/Fe3O4-SBA-15 hybrid was carried out using Fe3O4- SBA-15 as a hard template and sucrose as carbon precursor. Sucrose was dissolved in a solution of H2SO4 in water and to this solution, Fe3O4-SBA-15 was added. The resulting mixture was dried at 373 K and then heated at 433 K for 6 h. A second impregnation was performed in order to ensure the filling of the template pores with the carbon precursor. To obtain the carbon nanotubes, the sample was placed in muffle at 1173 K under nitrogen flow (20mL/min) for 30 min. In order to remove the silica, the material was placed in an HF solution. The CNTs was filtered, washed and dried at 323 K. In the present work, we report the synthesis and characterization of CNTs materials of hybrid material. The material was characterized by X-ray diffraction (XRD) and the morphologies and structural features of the prepared materials were observed from the SEM and TEM images.
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    Vanadium oxide supported on mesoporous SBA-15 modified with AI and Ga as a highly active catalyst in the ODS of DBT.
    (Univesidsad Tecnológica Nacional., 2017) Rivoira , Lorena Paola; Martínez , María Laura; Anunziata , Oscar Alfredo; Beltramone , Andrea Raquel; Anunziata , Oscar Alfredo; Martínez , María Laura
    In order to adapt current processes to the strict regulatory requirements, several technologies have been developed for deep desulfurization of diesel fuel. The major portion of sulfur in light cycle oils (LCO) is found in dibenzothiophene (DBT) and alkyl-dibenzothiophenes, which are not easily removable by hydrotreating, because they require high pressure and hydrogen consumption. Vanadium oxides supported on mesoporous SBA-15 catalysts with different vanadium loadings were studied in the oxidative desulfurization (ODS) of dibenzothiophene as a model sulfur compound. The catalytic activity was improved when SBA-15 framework was modified with Al and Ga as heteroatom substituting framework Si. Structural and textural characterization of the catalysts were performed by means of XRD, N2 adsorption, UV–Vis–DRS, XPS, NMR, TEM, Raman, TPR and Py-FTIR. UV–Vis–DRS and Raman demonstrated that highly dispersed vanadium VO4-3 species are responsible for the high activity in the sulfur removal. The Ga modified support with an intermediate V/Si ratio of 1/30 was the most active catalyst for ODS of DBT, using hydrogen peroxide as oxidant and acetonitrile as solvent. 100% of DBT elimination was attained at a short time in mild conditions. Gallium and aluminum incorporation into the support modified successfully the nature of the SBA-15 surface by generating Bronsted and Lewis acidity. The interaction between the acid sites with the active vanadium sites improved the activity of the catalysts. The high dispersion depended on the vanadium loading and on the nature of the support. The more acidic support allowed better dispersion of the vanadium species due to stronger interaction metal-support. The reusability of the catalysts indicates that vanadium oxide supported on mesoporous SBA-15 modified with Ga and Al are potential catalysts for the ODS of dibenzothiophene.
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    Vanadium oxide supported on mesoporous SBA-15 modified with AI and Ga as a highly active catalyst in the ODS of DBT.
    (Univesidsad Tecnológica Nacional., 2017) Rivoira , Lorena Paola; Martínez , María Laura; Anunziata , Oscar Alfredo; Beltramone, Andrea Raquel; Anunziata , Oscar Alfredo; Martínez , María Laura
    Vanadium pentoxide supported on mesoporous SBA-15 catalysts with different vanadium loadings were studied in the oxidative desulfurization (ODS) of dibenzothiophene as a model sulfur compound. The catalytic activity was improved when SBA-15 framework was modified with Al and Ga as heteroatom substituting Si. Structural and textural characterization of the catalysts were performed by means of XRD, N2 adsorption, UV–Vis–DRS, XPS, NMR, TEM, Raman, TPR and Py-FTIR. UV–Vis– DRS and Raman demonstrated that highly dispersed vanadium pentoxide crystallites are responsible for the high activity in the sulfur removal. The high dispersion depends on the vanadium loading and on the nature of the support. The more acidic support allowed better dispersion of the vanadium species. The Ga modified support with an intermediate V/Si ratio of 1/30 was the most active catalyst for ODS of DBT, using hydrogen peroxide (H2O2) as oxidant and acetonitrile as solvent. 100% of DBT elimination was attained at a short time in mild conditions. Gallium and aluminum incorporation into the support modified successfully the nature of the SBA-15 surface by generating Bronsted and Lewis acidity. The interaction between the acid sites with the active vanadium sites improved the activity of the catalysts. The reusability of the catalysts indicates that vanadium oxide supported on mesoporous SBA-15 modified with Ga and Al are potential catalysts for the ODS of dibenzothiophene.