FREIRE, V. A.; http://lattes.cnpq.br/6884779845218722; FREIRE, Vitória de Andrade.
Resumen:
The research on the development of micro-mesoporous structures has the
purpose of obtaining porous materials with superior characteristics, once it seeks
to join the high acidity of MCM-22 zeolite with the mesoporous system of MCM41
molecular sieve, consequently improving the diffusion of bulky molecules. In
this research, the following porous structures were synthesized: Initially, the
MCM-22-(P) lamellar precursor was obtained with molar ratio of SiO2\Al2O3 = 30
and was activated to obtain its MCM-22 zeolite form at 550 °C for 5 hours. Then,
MCM-22/MCM-41 micro-mesoporous material was synthesized by treating 2 g of
MCM-22 zeolite with a solution of 25 mL of 10% wt cetyltrimethylammonium
bromide (CTABr), where the material remained in an incubator at 110 °C for 7
days. In order to obtain a new material with better structural organization, the
MCM-22 was used in the following proportions (5%, 10% and 15%), remaining in
an incubator at 30 °C for 24 hours, being activated in air stream at 550 °C for 5
hours. The results of the X-ray diffraction characterization demonstrated the
MCM-22 (P) precursor formation and its MCM-22 zeolite form, with MWW
topology peaks. The curves obtained by means of the thermogravimetric analysis
(TG/DrTG), showed the losses of water mass and other adsorbates. The
micrographs (SEM) presented toroidal format with depreciation in the central
region for MCM-22. By means of the results of physical adsorption of N2, it was
verified for MCM-22 zeolites: type I isotherms and hysteresis loops of type-IV.
From the X-ray diffractograms for the micro-mesoporous materials, it was
possible to observe the formation of the porous structures, with the identification
of the reflection peaks pertinent to the microporous phase of MCM-22 and the
MCM-41 molecular sieve, coexisting in a single structural phase. The SEM
images detected the formation of particle agglomerates of the mesoporous phase
being constituted around the microporous phase. The textural analysis showed a
decrease in the volume of micropores and an increase in the volume of
mesopores, with type IV isotherms and hysteresis loops of type-II. Thus
demonstrating that the characterizations were effective in elucidating the porous
structures. It was possible to obtain the micro-mesoporous materials for both
methodologies, being the 5% content of MCM-22 zeolite the best synthesis
condition to obtain this new material.