Instituto de Química
URI Permanente desta comunidadehttps://repositorio.ufrn.br/handle/123456789/31488
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Navegando Instituto de Química por Autor "Alves, José Antônio Barros Leal Reis"
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Artigo Comparison of kinetic study of CTMA+ removal of molecular sieve Ti-MCM-41 synthesized with natural and commercial silica(ABM, ABC, ABPol, 2015) Melo, Marcus Antônio de Freitas; Fontes, Maria do Socorro Braga; Melo, Dulce Maria de Araújo; Costa, Cintia de Castro; Braga, Renata Martins; Alves, José Antônio Barros Leal ReisThis work aimed to determine and compare the apparent activation energy, involved in thermal decomposition of CTMA+ from the pores of Ti-MCM-41 synthesized by two different source of silica in order to evaluate their influence in the template removal. The molecular sieves Ti-MCM-41 were synthesized using rice husk ash (RHA), as alternative low cost source of silica, and commercial silica gel, obtaining two mesoporous material by hydrothermal synthesis of gel molar composition of: 1.0 CTMABr: 4.0 SiO2 : X TiO2 : 1.0 Na2 O: 200.0 H2 O. The samples were characterized to compare its properties by X-ray diffraction, IR spectroscopy, BET method and thermogravimetric analysis (TGA). The kinetic study using the model proposed by Flynn and Wall to determine the apparent activation energy for CTMA+ removal was performed using TGA data. The thermogravimetric analysis results of the material obtained from RHA confirmed intrinsic properties of mesoporous MCM-41 as the synthesized with commercial silica gel, such as high specific area, mesoporous range of pore diameter and hexagonal structure. According to the kinetics results the RHA showed similar chemical interaction to commercial silica gel, which makes it an interesting material, since it is a low cost source of natural silica from agricultural wasteArtigo Effect of the acid treatment of montmorillonite clay in the oleic acid esterification reaction(ABM, ABC, ABPol, 2015) Melo, Marcus Antônio de Freitas; Nascimento, Alexsandra Rodrigues do; Alves, José Antônio Barros Leal Reis; Melo, Dulce Maria de Araújo; Souza, Marcelo José Barros de; Pedrosa, Anne Michelle GarridoBiodiesel is a fuel renewable, biodegradable and environmentally correct fuel, which can be obtained from the esterification reactions, transesterification and pyrolisis. Montmorillonite is a clay mineral of the smectite group and are of great interest for industrial processes such as catalysis and adsorption. Acid activation of clay minerals is one of the most effective methods proposed to produce active materials. In this work, montmorillonite clay was treated with H2SO4 in different concentrations (0.2 – 0.8 mol L–1), characterized by X-ray diffraction (XRD), infrared spectroscopy (FT-IR) and applied in the catalytic esterification of oleic acid. The results reveal that the clay treated with aqueous solutions 0.8 mol L–1 H2SO4 shows promising catalytic activity toward the studied reaction, with maximum conversion of oleic acid of 65% at 30°CArtigo Unconventional silica source employment in zeolite synthesis: Raw powder glass in MFI synthesis case study(Elsevier, 2015-11-15) Vinaches, Paloma; Rebitski, Ediana Paula; Alves, José Antônio Barros Leal Reis; Melo, Dulce M. A.; Pergher, Sibele Berenice CastellãIn this work, the use of raw powder glass as a silica source was studied for silica MFI zeolite synthesis. The zeolite was successfully obtained by employing this silica source treated with a hydrochloric acid solution and as provided. Synthesis was performed using hydrofluoric acid as the mineralizing agent and tetrapropylammonium hydroxide as the organic structure-directing agent. Scanning electron microscopy micrographs revealed elongated crystals of larger size when the raw powder glass employed contained a lower silica percentage. X-ray diffraction patterns of the resulting products indicated that Fe-silicalite-1 was obtained and the Si/Fe ratio was calculated by interpolating the unit cell volume of the obtained zeolites in a linear regression created by employing literature data. The presence of iron was also confirmed by the presence of ν(Si–O–Fe)sym.str in the infrared spectra. Thermogravimetric analyses indicated good stability. This study concluded with a reproducible and optimized method for obtaining this versatile zeolite from raw powder glass with different compositions