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Ferrer V.,University of Zulia | Finol D.,University of Zulia | Solano R.,University of Zulia | Moronta A.,University of Zulia | Ramos M.,Instituto Zuliano Of Investigaciones Tecnologicas
Journal of Environmental Sciences (China) | Year: 2015

The catalytic activity of Pd catalysts supported on Ce0.73Tb0.27Ox/SiO2, Ce0.6Zr0.4Ox/SiO2, Ce0.73Tb0.27Ox/La2O3-Al2O3 and Ce0.6Zr0.4Ox/La2O3-Al2O3 was studied using the reduction of NO by CO. The catalysts were characterized by X-ray fluorescence, surface area, X-ray diffraction, temperature-programmed reduction, CO chemisorption and oxygen storage capacity. Temperature-programmed reduction results indicated that Tb or Zr incorporation improves the reducibility and oxygen storage capacity. CO chemisorption data suggested the presence of large PdO particles due to the low CO/Pd ratio. No significant differences were obtained in light off temperatures (TLight off) for all Pd catalysts and the most active was 1.5%Pd/Ce0.6Zr0.4Ox/SiO2. © 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Source


Avendano C.,Venezuelan Institute for Scientific Research | Briceno A.,Venezuelan Institute for Scientific Research | Mendez F.J.,Venezuelan Institute for Scientific Research | Brito J.L.,Venezuelan Institute for Scientific Research | And 4 more authors.
Dalton Transactions | Year: 2013

Novel MoO2/C nano/microcomposites were prepared via a bottom-up approach by hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of polyoxometalates (POMs: phosphomolybdic acid [H3PMo12O40] and ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O24] ·4H2O). The structural characterization by FT-IR, XRPD, SEM and TEM analyses revealed the controlled formation of hierarchical MoO 2/C composites with different morphologies: strawberry-like, based on carbon microspheres decorated with MoO2 nanoparticles; MoO 2/C core-shell composites; and irregular aggregates in combination with ring-like microstructures bearing amorphous Mo species. These composites can be fine-tuned by varying reaction time, glucose/POM ratio and type of POM precursor. Subsequent transformations in the solid state through calcinations of MoO2/C core-shell composites in air lead to hollow nanostructured molybdenum trioxide microspheres together with nanorods and plate microcrystals or cauliflower-like composites (MoO2/C). In addition, the MoO 2/C composite undergoes a morphology evolution to urchin-like composites when it is calcined under nitrogen atmosphere (MoO 2/C-N2). The MoO2/C strawberry-like and MoO2/C-N2 composites were transformed into Mo carbide and nitride supported on carbon microspheres (Mo2C/C, MoN/C, and MoN/C-N2). These phases were tested as precursors in thiophene hydrodesulphurization (HDS) at 400°C, observing the following trend in relation to the thiophene steady-state conversion: MoN/C-N2 > MoN/C > Mo2C/C > MoO2/C-N2 > MoO 2/C. According to these conversion values, a direct correlation was observed between higher HDS activity and decreasing crystal size as estimated from the Scherrer equation. These results suggest that such composites represent interesting and promising precursors for HDS catalysts, where the activity and stability can be modified either by chemical or structural changes of the composites under different conditions. © 2013 The Royal Society of Chemistry. Source


Colina R.,University of Zulia | Primera J.,University of Zulia | Ysambertt F.,University of Zulia | Plaza E.,Instituto Zuliano Of Investigaciones Tecnologicas | Huerta L.,University of Zulia
Revista Tecnica de la Facultad de Ingenieria Universidad del Zulia | Year: 2013

Gels with a TEA/Si ratio of 1 (G1) were synthesized by atrane way. The microwave extraction of organic matter in these gels was performed varing type of solvent, power and exposure time to microwaves. Monitoring the influence of these parameters was realized by loss mass percentage in solids, infrared spectroscopy (IR) and thermodifferential analysis. Water was the most suitable solvent for the organic matter extraction, and a power of 80% (560 W) with 120 seconds as the optimal values for extraction, with extraction porcentage of 100%. A sample gel was calcined, and characterized by adsorption-desorption isotherm of N2 at 77 K, IR and SEM as comparison bases. The adsorption- desorption isotherm is of IV type, with a surface area of 694 m2/g, pore volume of 0,86 cm3/g y average pore diameter of 4,84 nm. The loss mass percentage of this gel was 95%. Source


Mendez F.J.,Venezuelan Institute for Scientific Research | Llanos A.,Instituto Universitario Of Tecnologia Dr Federico Rivero Palacio | Echeverria M.,Venezuelan Institute for Scientific Research | Echeverria M.,Instituto Universitario Of Tecnologia Dr Federico Rivero Palacio | And 8 more authors.
Fuel | Year: 2013

(Figure Presented) A series of tungsten and molybdenum catalysts supported on MCM-41 were prepared using Keggin heteropolyacids (H3PM 12O40, M = Mo or W) as active phase sources and compared with their analogues unsupported. The physicochemical characterization was carried out by, small angle and wide angle X-ray diffraction; thermogravimetric analysis/differential scanning calorimetry; ultraviolet-visible diffuse reflectance and Fourier transform infrared spectroscopies; N2 physisorption and potentiometric titration with N-butylamine, for determination, respectively, of the structure; thermal stabilities; integrity of heteropolyacids; textural properties and superficial acidity. The solids were tested in the thiophene hydrodesulfurization reaction at 400°C, atmospheric pressure and weight hourly space velocity of 0.48 h-1. In this study, it has been demonstrated the importance of supporting heteropolyacids to increase the catalytic activity. Furthermore, it was proved a correlation between surface acidity and calcination temperature with the activity and stability of these catalysts in the hydrodesulfurization reaction. © 2012 Elsevier Ltd. All rights reserved. Source


Morales-Toyo M.,Venezuelan Institute for Scientific Research | Alvarado Y.J.,Venezuelan Institute for Scientific Research | Restrepo J.,Venezuelan Institute for Scientific Research | Seijas L.,University of Los Andes, Venezuela | And 2 more authors.
Journal of Chemical Crystallography | Year: 2013

Derivatives hydrazone are attributed interesting pharmacological properties. The compound under study (E)-ethyl 4-(2-(thiofen-2-ylmethylene) hydrazinyl)benzoate (1), crystallized from ethanol as translucent light yellow thin plates. They are monoclinic, space group P21/c, with unit cell parameters a = 8.846(6), b = 20.734(14), c = 7.583(5) Å, β = 95.743(13), V = 1383.8(16) Å3. Three hydrogen bonds and two intermolecular π-interaction perpendiculars to the hydrogen bonds patterns are observed in the crystal structure. A detailed description of these interactions will be presented. Also, semiempirical calculations (PM6) show the formation in the gas phase of a supramolecular chain, emulating the C(8) graph set seen in the crystal structure of the compound. Graphical Abstract: The synthesis and crystal structure of the title compound, C14H 14N2O2S, is reported.[Figure not available: see fulltext.] © 2013 Springer Science+Business Media New York. Source

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