Effect of thermal treatment and direct tungstophosphoric acid addition on the characteristics of urea-templated titania

V. FUCHS; MIRTA NOEMÍ BLANCO; L. R. PIZZIO

Seoul, Corea del Sur

Congreso; 14th International Congress on Catalysis; 2008

Catalysis Division of the KIChE

Urea-templated titania directly modified with tungstophosphoric acid (TPA) was synthesized via HCl catalyzed sol-gel reaction, with TPA amount of 20 % w/w, and was thermally treated at 100, 200, 300, 400, 500, and 600°C. Mesoporous materials were obtained, with average pore diameter higher than 3.1 nm. The specific surface area SBET decreased and the mean pore radius increased with the calcination temperature, effect less marked for the sample with TPA addition. XRD patterns showed the presence of anatase phase, though a partial transformation into rutile took place at 600 ºC. The crystallinity and particle size increased with calcination temperature, the increment being lower when TPA is added. TEM images showed spherical particles of 5-60 nm size; the agglomerates formed increased their size with temperature. According to FT-IR and 31P MAS-NMR, TPA Keggin structure is preserved during synthesis and calcination. The DRS spectra displayed an absorption threshold onset that shifts to visible region with temperature increase and TPA addition. The band gap energy decreased as a result of TPA introduction into the TiO2 matrix and, in a lesser extent, with calcination temperature increase. The new synthesized materials could be good catalysts for photodegradation reactions.