Síntese e caracterização de titanatos lamelares impregnados com Mg2+/MgO ou La3+/La2O3 e sua utilização em reações de transesterificação
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2010-10-01
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Universidade Federal de Goiás
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Potassium tetratitanate (K2Ti4O9) and sodium trititanate (Na2Ti3O7) were
synthesized by solid state reaction at 800°C and wet impregnated using
Mg2+/La3+ or nanoparticles of MgO/La2O3 varying ion/oxide content in 1, 5 or
10% of matrix weight. MgO and La2O3 synthesized by precipitation method and
their mean crystallite size calculated in 11 nm and 72 nm, respectively.
Synthesized materials were characterized by X ray diffractometry,
termogravimetry, N2 adsorption, mid-infrared spectroscopy, transmission
electron microscopy and they were applied on transesterification reactions
using mixtures of methyl acetate/ethanol and ethyl acetate/methanol. Interlayer
distance calculated for solids is about 8 Å. Impregnation of ion/oxide in matrices
K2Ti4O9 and Na2Ti3O7 produced structural changes like loss of crystallinity for
some of them including peak broadening or disappearing. All synthesized
materials, after burning in an atmosphere of N2 (g), lost mass related to the exit
of surface water and interlamellar water. Materials showed low surface area,
with values below 5 m2/g. In general, powder utilized had conversion rates
between 10 and 80%. Emphasis should be given to pure matrices which
presented conversions rates equal or higher than impregnated powders, and
the use of matrix K2Ti4O9 led to better results. Among the oxides chosen for
impregnation, higher efficiency was observed for MgO. Some powders were
reused for the same reactions and its activity decreased in each reaction cycle.
Reaction mixture analysis after reuse tests to K2Ti4O9 revealed partial leaching
of K+ ions, however XRD patterns profile analysis did not show structural
changes occurrence. A proposal to explain layered titanate activity on
transesterification reactions is made based on acid-base properties of layers
and output of K+ from interlamellar area.
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SANTOS, R. L. Síntese e caracterização de titanatos lamelares impregnados com Mg2+/MgO ou La3+/La2O3 e sua utilização em reações de transesterificação. 2010. 55 f. Dissertação (Mestrado em Química) - Universidade Federal de Goiás, Goiânia, 2010.