Nano silica particles arranged as blackberry like mesoporous structures modified with tungstophosphoric acid

A. SOSA; M. BLANCO; L. PIZZIO

Washington D.C.

Conferencia; NanoTech 2015, Advanced Materials & Applications, TechConnect World Innovation Conference; 2015

TechConnect

Silica nano particles arranged as blackberry like mesoporous structures were successfully prepared in a water/oil phase using organic templates method and impregnated with tungstophosphoric acid (TPA) solutions. The preparation method involves the simultaneous hydrolytic condensation of tetraorthosilicate to form silica and the polymerization of styrene, lysine as acid catalyst, octane hydrophobic-supporting reaction component, and cetyltrimethylammonium bromide surfactant were used. After that, organic components were removed by calcination. Finally, they were modified with TPA at 30% (w/w) and annealed at 200-500 ºC. Materials were characterized by scanning and transmition electron microscopy (SEM and TEM), FT-IR spectroscopy, X-ray diffraction (XRD), 31P magic angle spinning-nuclear magnetic resonance (31P MAS-NMR). N2 adsorption-desorption isotherms were perform to estimate the specific surface area and mean pore size (SBET = 421 m2/g and DP = 14 nm respectively). According to SEM and TEM results blackberry like silica structures (with a mean diameter of 30 nm) were formed by the arrangement of spherical silica particles (5nm). FT-IR and 31P MAS-NMR results revealed that the main species present in the silica TPA impregnated samples is the [PW12O40]3- anion. The number of acid sites and their acid strength were measured and they depend on the thermal treatment temperature used.