Estudo da influência de organosilano na obtenção de zeólitas nanoestruturadas

• Ano de defesa: 2019
• Autor(a) principal: Cysneiros, Olívia Maria Silvestre
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Alagoas; Brasil; Programa de Pós-Graduação em Engenharia Química; UFAL
• Palavras-chave em Português: Zeolitas – Porosidade; Nanoestruturas; Silica; Zeolites – Porosity; Nanostructures; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA
• Link de acesso: http://www.repositorio.ufal.br/handle/riufal/5532

The work proposed a direct method for the generation of secondary porosity in zeolites mordenite and ferrierite, obtained through the addition of organosilane to the synthesis gel. The synthesis of the zeolites in question was carried out by means of the hydrothermal method, and the influence of the organosilane as mesoporosity generating agent was analyzed with the addition of dimethyl octadecyl [3- (trimethoxysilyl) propyl] ammonium chloride (TPOAc) chloride solution in the (XRD), nitrogen adsorption at -196°C, thermogravimetric analysis (ATG / DTG), absorption spectroscopy in the infrared region with Fourier Transform (FT- IR), ammonia desorption at programmed temperature (TPD-NH3) and scanning electron microscopy (SEM). The diffractograms of the obtained materials showed peaks corresponding to the reference structure, but in 192 hours of crystallization for sample of ferrierite with addition of TPOAc complete conversion to mordenite occurred. The extended peaks observed in the diffractograms made the sample of mordenite using TPOAc, with 96 hours of crystallization, a possible candidate for nanostructured zeolite, followed for later characterizations. The sample of mordenite with addition of silanizing agent related to 96 hours of crystallization presented high external area, as well as greater area and volume of mesopores, guaranteeing the additional mesoporosity, whereas for ferrierite synthesized with organosilane for 96 hours the extinction of micropores of the structure, not obtaining a secondary porosity. The thermogravimetric curves of the samples obtained with silane showed four mass loss events and a greater loss compared to the standard samples. The absorption spectra in the infrared region showed the same absorption bands, and there was a change in their intensity. The desorption profiles of NH3 indicated very similar behaviors between the mordenite sample with organosilane and its respective standard, although the addition of silane promoted the reduction of acidic sites of the sample. The micrographs ensured the obtaining of nanometric crystals formed by spherical agglomerates resulting in mordenite nanozeolite, whereas for ferrierite sample the crystals presented superior dimensions. Therefore, the crystallization of mordenite at 140°C for 96 hours favors mesoporosity secondary to the zeolite structure, in addition to nanometric crystals with properties superior to ferrierite under the same conditions.