Navegando por Autor "Rojas, Leopoldo Osvaldo Alcazar"

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LayCu0.4Fe0.6O3 perovskite oxides: synthesis, characterization and catalytic reactivity in the fischer-tropsch synthesis
(Brazilian Association of Research and Development in Petroleum and Gas (ABPG), 2011) Melo, Marcus Antônio de Freitas; Souza, José Roberto de; Silva, C. F.; Melo, Dulce Maria de Araújo; Rojas, Leopoldo Osvaldo Alcazar; Oliveira, F. S.
The current natural gas production of 52 Mm3 d-1 and the large projects for its expansion has been setting new boundaries for the Brazilian industry of oil and gas. So far, one of the biggest challenges regards the logistics for gas transportation from offshore fields. Therefore, the transformation of natural gas into gasoline, diesel and/or olefins via Fischer-Tropsch synthesis would be an alternative to this matter. In this work, the production of hydrocarbons by Fischer-Tropsch synthesis in a slurry reactor was investigated and a perovskite-type catalyst (LayCu0,4Fe0,6O3) was used, where the lanthanum index “y” varies from 0 to 1 on a molar basis. The selection of the method to synthesize perovskite largely depends on its target application and desired properties. The synthesized perovskites were characterized by X-ray diffraction (XRD) and energy dispersive X-ray fluorescence (EDX). The reducibility of such oxides was studied by a temperature-programmed reduction (TPR) technique and the reactivity of the catalysts was evaluated in a slurry reactor. The selectivity toward hydrocarbons was better in materials with a lanthanum content ranging between 0.6 and 0.8 to produce hydrocarbons (C1-C6 and C17-C26) from syngas by the Fischer-Tropsch (FT) synthesis
Oxidación húmeda de fenoles con catalizadores Fe-CeO2, K-MnO2/ CeO2/Paligorsquita y Fe/ paligorsquita
(Centro de Información Tecnológica, 2011) Santiago Júnior, Aristides Felipe; Sousa, João Fernandes de; Benachour, Monhad; Rojas, Leopoldo Osvaldo Alcazar
Se ha evaluado el funcionamiento de catalizadores Fe-MnO2/CeO2, K-MnO2/CeO2/Paligorsquita y Fe/Paligorsquita en la degradación oxidativa húmeda del fenol en un reactor de mezcla. Los experimentos se ejecutaron a: temperatura de 130º C, presión de 20.4 atm., concentración másica del catalizador de 5 g/L y concentración inicial del fenol de 0,5 g/L Los parámetros evaluados fueron: contenido de hierro impregnado (0, 3; 7 y 10%, m/m) y el pH inicial del medio reactivo (3.1; 6.8 y 8.7). Las curvas de degradación del fenol indican que el catalizador Fe+2/Paligorsquita tiene un papel preponderante en la conversión de carbono orgánico total comparado con los demás catalizadores. Se encontró también que la disminución de la alcalinidad del medio reactivo favorece la conversión de fenol y que el soporte paligorsquita parece ser más resistente a la acción de los compuestos ácidos formados durante la reacción
Synthesis and characterization of bifunctional transition-metal/silica-alumina catalysts for the chloromethane conversion to hydrocarbons
(ABPG, 2008) Rojas, Leopoldo Osvaldo Alcazar; Nascimento, José Carlos; Ruiz, Juan Alberto Chavez; Benachour, Monhad; Sousa, João Fernandes de
In this work bifunctional (metal-acid) catalysts of Fe, Ni, Fe2O3 and NiO over amorphous silica alumina support were characterized (acidity) and evaluated for the conversion of chloromethane in a fixed bed reactor. Temperature program tests TPD (Temperature Programmed Desorption) and TPR (Temperature Programmed Reduction) were performed to characterize the quimissorption sites for the impregnated and unimpregnated support. New adsorption sites were created on the metal supported catalysts. The conversion yield of chloromethane was evaluated for the five materials. The highest conversion conversion (85%) was observed for the unmodified support (SiAl) after 6 of reaction at 860 K and a WHSV (Weight Hourly Space Velocity) of 4,5 h-1. The best selectivity toward desirable hydrocarbons (C3, C4) was found for the Fe-SiAl catalyst. C3 was also found in the products stream when Ni/SiAl and NiO/SiAl catalyts were tested. Ni catalysts were the most favorable to methane production. The catalytic tests showed coke formation in all materials. For the SiAl support the desorption energy of chloromethane, determined by TPD runs, was 101,9 KJ/mol. The metals presented lower desorption energies (75,2 KJ/mol for Ni and 133,4 KJ/mol for Fe) than the oxides (190,1 KJ/mol for Fe2O3 and 322,4 KJ/mol for NiO)
Synthesis and characterization of CuCl2/SiO2 catalyst for the oxychlorination of methane
(Brazilian Association of Research and Development in Petroleum and Gas (ABPG), 2011) Nascimento, José Carlos; Sousa, João Fernandes de; Rojas, Leopoldo Osvaldo Alcazar; Fontes, Francisco de Assis Oliveira
CuCl2 catalysts supported on silica were used in the oxychlorination of methane. The materials were synthesized by the ion-exchange technique in a basic solution, using a copper-ammonia complex with 3 and 6 % of nominal copper load. The materials where characterized by Thermogravimetry (TG), X-ray Fluorescence Spectroscopy (XRF), Temperature Programmed Reduction (TPR), Scanning Electron Microscopy with X-ray microanalysis (SEM/EDS), BET specific area, and Pore Distribution. The characterization confirmed the presence of copper on the support surface, concluding that the ion-exchange technique was adequate for the catalyst synthesis. During reaction assays, an oxychlorination bench-scale unit was employed. The tests were carried out at 673 and 773 K. The results demonstrated the influence of temperature and catalyst copper content on methane conversion
Total catalytic wet oxidation of phenol and its chlorinated derivates with MnO2/CeO2 catalyst in a slurry
(Brazilian Society of Chemical Engineering, 2009-09) Luna, A. J.; Rojas, Leopoldo Osvaldo Alcazar; Melo, Dulce Maria de Araújo; Benachour, Monhad; Sousa, João Fernandes de
In the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO). A mixed oxide of Mn-Ce (7:3), the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl2 and CeCl3 in a basic medium. The mixed oxide, MnO2/CeO2, was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC and pressure of 2.04-4.76 MPa. A phenol solution containing 2.4-dichlorophenol and 2.4-dichlorophenoxyacetic acid was also degraded with good results. A lumped kinetic model, with two parallel reaction steps, fits precisely with the integrated equation and the experimental data. The kinetic parameters obtained are in agreement with the Arrhenius equation. The activation energies were determined to be 38.4 for the total oxidation and 53.4 kJ/mol for the organic acids formed

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Navegando por Autor "Rojas, Leopoldo Osvaldo Alcazar"