Navegando por Autor "Souza, M. J. B."
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Artigo Structural and morphological characterization of Pt/WOx–ZrO2 Catalysts(Springer, 2008-08-09) Melo, Marcus Antônio de Freitas; Pedrosa, Anne Michelle Garrido; Melo, Dulce Maria de Araújo; Souza, M. J. B.; Araújo, Antônio S.; Lima, S. H.; Sasaki, José MarcosCatalysts of Pt/WOx–ZrO2 type with 1 wt% of Pt and 10, 15 and 20 wt% of tungsten were synthesized and characterized. The structural and morphological features of these catalysts were studied. The samples were synthesized by impregnation method and calcined at 600 C, 700 C and 800 C. The characterizations were carried out using different techniques: X-ray diffraction, Raman spectroscopy, scanning electronic microscopy, nitrogen adsorption measurement and refinement of their crystalline structures by Rietveld method. X-ray diffraction patterns revealed the formation ZrO2 and WO3 crystalline structures and its crystallite size were determined. The zirconium oxide crystallized into tetragonal and monoclinic phases and tungsten trioxide crystallized into monoclinic phase. Crystalline WO3 and amorphous WOx species were detected by Raman spectraArtigo Synthesis, optimization and characterization of zeolite beta (BEA): production of ZSM-5 and NaAlSiO4 as secondary phases(Editoria da RVq - Editoria da RVq - PubliSBQ, 2017) Melo, Marcus Antônio de Freitas; Nascimento, Alexsandra Rodrigues do; Figueredo, Gilvan Pereira de; Silva, E. M. F.; Melo, Dulce Maria de Araújo; Souza, M. J. B.The choice of synthesis parameters influences obtainment of a suitable material for use in several applications. In this paper, zeolite beta (BEA) was successfully obtained by hydrothermal synthesis, assessing the following parameters: Si/Al ratio, time and crystallization temperature. The synthesized materials were characterized by X-ray diffraction (XRD), Fourier-Transfer Infrared (FTIR) spectroscopy, thermogravimetry (TG and DTG) and N2 adsorption-desorption isotherm analyses. X-ray diffraction showed that the change of only one of these parameters acts on the formation of the desired microporous structure. BEA was obtained in the Si/Al ratio equal 8, with a crystallization time of 4 days at 170 °C, presenting a specific area of 437 m2 g-1 and a pore volume of 0.106 cm3g-1. In other assays, secondary phases of NaAlSiO4 and SiO2 were obtained, as well as ZSM-5 zeolite, analcime, omega and linde B2