Navegando por Autor "Vinaches, Paloma"
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Artigo An Introduction to Zeolite Synthesis Using Imidazolium-Based Cations as Organic Structure-Directing Agents(MDPI, 2017-08-06) Pergher, Sibele Berenice Castellã; Vinaches, Paloma; Gusmão, Katia BernardoZeolite synthesis is a wide area of study with increasing popularity. Several general reviews have already been published, but they did not summarize the study of imidazolium species in zeolite synthesis. Imidazolium derivatives are promising compounds in the search for new zeolites and can be used to help understand the structure-directing role. Nearly 50 different imidazolium cations have already been used, resulting in a variety of zeolitic types, but there are still many derivatives to be studied. In this context, the purpose of this short review is to help researchers starting in this area by summarizing the most important concepts related to imidazolium-based zeolite studies and by presenting a table of recent imidazolium derivatives that have been recently studied to facilitate filling in the knowledge gapsArtigo Introduction of Al into the HPM-1 framework by in situ generated seeds as an alternative methodology(MDPI, 2018-09-13) Pergher, Sibele Berenice Castellã; Vinaches, Paloma; Rojas, Alex; Alencar, Ana Ellen V. de; Castellón, Enrique Rodríguez; Braga, Tiago P.An alternative method for the introduction of aluminum into the STW zeolitic framework is presented. HPM-1, a chiral STW zeolite with helical pores, was synthesized in the pure silica form, and an aluminum source was added by in situ generated seeds. Displacements of the peak positions in the Al samples were found in the X-ray diffractograms, indicating the possible incorporation of the heteroatom into the framework. Using an analysis of the 29Si and 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra, we concluded that the aluminum was effectively introduced into the framework. The (AlTETRAHEDRAL/AlOCTAHEDRAL) ratio and its textural properties were studied to explain the catalytic ethanol conversion results at medium temperatures. The sample with the lowest Si/Al ratio showed the best results due to its higher surface area and pore volume, in comparison to those observed for the sample with the highest Si/Al ratio, and due to its higher bulk tetrahedral aluminum content, in comparison to the intermediate Si/Al ratio sample. All catalysts were selective to ethylene and diethyl ether, confirming the presence of acidic sitesArtigo Organic structure-directing agents in SAPO synthesis: the case of 2-ethyl-1,3,4-trimethylimidazolium(Wiley, 2018-01-23) Pergher, Sibele Berenice Castellã; Vinaches, PalomaStructure direction is a key topic in zeolite synthesis. In this work, the organic cation 2‐ethyl‐1,3,4‐trimethylimidazolium was studied for the first time in the synthesis of SAPO zeolite. Concentrated gels and fluoride media were chosen for the synthesis. To understand the formation of the main products, CHA and LTA zeotypes, several statistical calculi were performed, and the results showed that the structure direction of the LTA zeotype was mainly caused by to the organic cation. For SAPO‐CHA, the temperature and a combination of dilution and synthesis time also influenced the formation. The CHA zeotype was studied thoroughly by other techniques such as thermogravimetry, high‐power decoupled (HPDEC) magic‐angle spinning (MAS) NMR spectroscopy, and nitrogen sorption. We calculated that this zeotype contains one cation per unit cell and observed that the fluoride medium also directs the structure. The silicon atoms in SAPO‐CHA are present in three states [SiO(4X), SiO(3X), and SiO(1X)], aluminium atoms were found in tetrahedral and octahedral coordination environments, and the phosphorus atoms also had tetrahedral geometries. Textural analysis confirmed the formation of a microporous material with a Brunauer–Emmett–Teller (BET) surface are of 510 m2 g–1 and an external surface of 110 m2 g–1Artigo Raw powder glass as a silica source in the synthesis of colloidal MEL zeolite(Elsevier, 2016-09-01) Pergher, Sibele Berenice Castellã; Vinaches, Paloma; Alves, José Antônio B. L. R.; Melo, Dulce Maria de AraujoColloidal MEL zeolite was successfully synthesized using raw powder glass as a new silica source at 114 and 150 °C. Tetrabutylammonium hydroxide and hydrofluoric acid were used and hydrothermal synthesis was performed. Results concluded that the samples have plate-like morphologies in both synthesis conditions. Thermogravimetric analysis showed that they are stable and their sorption isotherms shapes coincided with the reportedArtigo 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 compositionsArtigo Zeolite synthesis in basic media using expanded perlite and its application in Rhodamine B adsorption(Elsevier BV, 2018-09-15) Pergher, Sibele Berenice Castellã; Silva Filho, Severino H. da; Vinaches, PalomaIn this work, expanded perlite was employed as a Si and Al source in zeolite synthesis. The products obtained were mixtures of three zeolitic topologies identified by X-ray diffraction and scanning electron microscopy. The zeolite OFF presented elongated prism morphology and the zeolites GIS and ERI appeared as crystal intergrowths. The products and the expanded perlite were used in a Rhodamine B adsorption study . The zeolitic mixture turned out to be a better adsorber than the expanded perlite, obtaining an efficiency of 90% up to 2 min and an equilibrium efficiency of 72% after 5 min