Sintese e caracterização de titanoaluminofosfatos mesoporosos, meso-TAPO

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The aim of this Dissertation is the synthesis and characterization of molecular sieves with an inorganic titaniumaluminumphosphates framework and a mesoporous structure. For the synthesis of such materials, two experimental approaches were investigated, based on previous experiments that determined the initial parameters for the hydrolysis of the titanium source, titanium isopropoxide. For both synthetic routes the templating agent of choice was cetyltrimethylammonium bromide (CTAB) in the presence of tetramethylammonium hydroxide (TMAOH). The organic templating agent for the composites obtained in both synthetic routes was removed through Soxhlet extraction form diluted isopropylamine-ethanol solution, followed by calcining. The first synthetic route studied used aluminum isopropoxyde as the source for such element. Two experimental parameters where investigated: the pH, acquiring values in the range between 10.5 and 11.5, and the TiO2/AI2O3 molar ratio, varing between 0.03 and 0.14. The second experimental strategy investigated the synthesis of analogous titaniumaluminumphosphates utilizing an inorganic source for the aluminum ions, namely aluminum sulfate. The characterization of the solids obtained in this work was performed by X ray diffractometry, elemental analysis, diffuse reflectance UV-Vis spectroscopy, infrared absorption spectroscopy, AI, P and C solid state nuclear magnetic resonance and transmission electron microscopy. The hexagonal mesostructure was characterized in the as-synthesized solids, for both synthetic strategies, by the presence of two diffraction signal in the small angle region characteristic of a hexagonal packed channel structure. The method of insertion for titanium (IV) in the inorganic framework was investigated in this Dissertation. The addition of peroxytitanic acid to the synthesis gel results in incorporation of titanium in isolated sites in the inorganic framework, as suggested by UV-Vis spectroscopy data. Such features, in association with a simpler experimental procedure and low cost introduced by the use of inorganic aluminum precursors, set these materials as a potential catalyst for redox reactions.

ASSUNTO(S)

titanio peneiras moleculares

ACESSO AO ARTIGO

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