Browsing by Author "Vallés, Verónica Alejandra"

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    Catalytic oxidation of sulfur compounds over Ce-SBA-15 and Ce-Zr-SBA-15
    (2021) Rivoira, Lorena Paola; Vallés, Verónica Alejandra; Martínez, María Laura; Yanika, Sa-ngasaeng; Siriporn, Jongpatiwut
    The catalytic oXidation of different sulfur compounds, commonly present in liquid fuel, was studied over a series of ceria and ceria-zirconium based oXidation mesoporous catalysts. SBA-15 was synthesized using sol-gel method and Ce and Ce-Zr were added by two different procedures: i) directly during the synthesis and ii) via post- synthesis method. The catalysts were characterized by XRD, N2 adsorption isotherms, XPS, DRUV-Vis, TEM, SEM and Py-FTIR. Low angle XRD, N2 isotherms and TEM confirmed that the structure was not changed after metal incorporation. Wide angle XRD, UV–vis-DRS, XPS and TEM determined that the catalysts prepared by direct synthesis presented higher dispersion of Ce oXides, smaller particle size and isolated Zr4+ species. FTIR of adsorbed/desorbed pyridine indicated that zirconium as promoter increases the Lewis acidity of the catalysts, especially during direct synthesis. Ce-Zr-SBA-15 catalyst prepared by direct synthesis was very active in the oXidation of dibenzothiophene, 4,6-dimethyl dibenzothiophene and benzothiophene using hydrogen peroXide (H2O2) as oXidant agent and acetonitrile as polar solvent. The effect of acidity in the catalyst, hydrogen peroXide concentration and temperature was studied. The deactivation test demonstrated that the catalyst is stable and adequate for the industrial process.
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    HDT of the model diesel feed over Ir-modified Zr-SBA-15 catalysts
    (2018) Vallés, Verónica Alejandra; Yanika, Sa-ngasaeng; Martínez, María Laura; Siriporn, Jongpatiwut; Beltramone, Andrea Raquel
    Iridium catalyst using different zirconium modified-SBA-15 supports were tested in the HDT of tetralin and typical sulfur and nitrogen compounds present in diesel feed. The zirconium modified-SBA-15 supports were synthesized by sol-gel method using two sources of zirconium, zirconyl chloride and zirconium (IV) propoXide. Regarding XRD, N2 adsorption isotherms and TEM, we obtained better textural and structural properties using the alkoXide, especially when lactic acid was added in order to decrease the hydrolysis rate of zirconium propoXide. In addition, XPS and DRUV-Vis demonstrated that zirconium was incorporated mainly as tetrahedral Zr4+ species NH3-TPD showed that higher acidity is observed when tetrahedral Zr4+ species are present. Iridium dispersion was determined by TEM and H2-chemisorption and reducibility by XPS and TPR. Among the catalysts prepared, the catalyst synthesized using zirconium propoXide and lactic acid presented the highest dispersion, lowest cluster size and lowest reduction temperature. Consequently, this was the most active catalyst for the hydrogenation of tetralin, the HDN of indole and quinoline and the HDS of dibenzothiophene (DBT) and 4,6- dimethyldibenzothiophene (4,6-DMDBT). The presence of Zr+4 had a remarkable effect on the dispersion and reducibility capacity of the iridium actives species. In addition, the presence of moderate acidity in this material gives the best catalyst for HDN and HDS in the studied conditions. The inhibition effect of the sulfur and nitrogen compounds over tetralin hydrogenation was studied using individual feeds and a miXture feed. We observe that 4,6-DMDBT and quinoline were the most refractory compounds and they showed the highest inhibition effect. Tetralin hydrogenation was stronger inhibited when using the miXture feed compared with the individual feeds. This can be explained in terms of the competition between the different compounds that retard the rate of hydrogenation of tetralin. However, a high conversion of tetralin was achieved even when 300 ppm of S or N was
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    HDT process performance over noble metal-mesoporous catalysts
    (2022) Vallés, Verónica Alejandra; Ledesma, Brenda Cecilia; Beltramone, Andrea Raquel
    The greater concentration of market demand in the diesel range forces refiners to consider redirecting internal refinery cuts to new hydrocracking units to increase the contribution to the gasoline and diesel pool. These requirements drive advances particularly in hydrotreating technologies (HDT). The need to reduce the level of sulfur and polyaromatics in diesel fuel to values ??of a few ppm and the need to process heavy cuts with a high degree of aromaticity has motivated the appearance of new, more efficient processes. In recent years, bimetallic catalysts have received much attention, since they can combine two or more functions. The functionality of a catalyst can be due to active sites generated by supported metals and the interaction with the support. Pt-Pd catalysts have been extensively studied in order to improve tolerance to sulfur and other contaminants. They showed higher activity, stability and resistance to poisons compared to monometallic Pt or Pd catalysts. In bimetallic catalysts, the formation of the alloy creates electrondeficient species, more resistant to poisoning, in the case of Pd, which alone or alloyed with Pt, has a high hydrogenating and thio-resistant capacity and has begun to be used in industrial dearomatization units. The objective of this work is to evaluate the activity of all the synthesized catalysts in typical catalytic hydrotreating reactions. Performing first a kinetic study in a Batch reactor to the best catalysts that will then be tested in a continuous flow reactor in operating conditions close to industrial ones. With this objective, catalysts supported on SBA-16 were synthesized. This mesoporous has a high surface area and good characteristics of thermal stability, against the conditions set. The support was modified by incorporating Al indirectly and then impregnated with Ir, Pt and Pd. The behavior of the synthesized catalysts was studied against a commercially used catalyst and another support widely used in the industry, such as alumina. The catalysts were characterized by XRD, FTIR, NMR, TPR and N2 adsorption- desorption isotherms.
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    Magnetic Fe3O4@SiO2–Pt and Fe3O4@SiO2–Pt@SiO2 structures for HDN of indole
    (2019) Dinamarca, Robinson; Vallés, Verónica Alejandra; Ledesma, Brenda Cecilia; Campos, Cristian H.; Pechci, Gina
    The effect of a second porous SiO2 shell in the activity and selectivity of the Fe3O4@SiO2–Pt catalyst in the hydrodenitrogenation of indole is reported. The double Fe3O4@SiO2–Pt@SiO2 structure was prepared by coating Fe3O4 nanoparticles with tetraethyl orthosilicate (TEOS) with a further impregnation of 1.0 wt.% of Pt on the (3-aminopropyl)triethoxysilane functionalized Fe3O4@SiO2 structures. The second porous SiO2 shell, obtained by using a hexadecyltrimethylammonium bromide (CTAB) template, covered the Fe3O4@SiO2–Pt catalyst with a well-defined and narrow pore-sized distribution. The full characterization by TEM, inductively coupled plasma-optical emission spectroscopy (ICP-OES), XRD, and N2 adsorption isotherm at 77 K and vibrating sample magnetometry (VSM) of the catalysts indicates homogeneous core@shell structures with a controlled nano-size of metallic Pt. A significant effect of the double SiO2 shell in the catalytic performance was demonstrated by both a higher activity to eliminate the nitrogen atom of the indole molecule present in model liquid fuel and the improvement of the catalytic stability reaching four consecutive reaction cycles with only a slight conversion level decrease.