Papers by Author: P. Del Angel

Abstract: Nanocrystalline TiO2 powders were prepared by the sol-gel method and evaluated in the NO photocatalytic oxidation. Samples annealed at 200 and 500°C (TiO2-P-200, TiO2-P-500) were characterized by nitrogen adsorption, XRD-Rietveld refinements, TEM, FTIR and UV-vis spectroscopies. The photocatalytic test of the sol-gel TiO2 samples was carried out in an insulated chamber with 10 ppm of NO, using a 365-nm UV light lamp; the test results were compared with those obtained with a commercial catalyst (P25). Improved photoactivity (89 % of NO oxidized in 60 min) was obtained with the TiO2-P-200 solid which showed high surface area, small crystallite size, higher amount of OH and highly abundant brookite phase (37.2 %) coexisting with the anatase phase (62.8 %). The photo-oxidation activity of the sol-gel catalyst annealed at 500 °C (TiO2-P-500) showed changes in its textural and morphologic properties and therefore, less photoactivity. Sol-gel photocatalysts could be a good option for abating pollution in both indoor and outdoor environments at room temperature.

Abstract: Mesoporous zirconia-Mn oxides were prepared by surfactant-assisted precipitation using different zirconia precursors and cetyl-trimethyl-ammonium bromide (CTAB) as a synthetic template. The objective of this work was to find out the influence of the zirconia precursors over the structural and textural characteristics of Mn-doped mesoporous zirconia solids. A series of syntheses were carried out by two methods using different zirconia precursors, modifying the Zr:surfactant ratio and the hydrolysis rate of the precipitate. After calcination at 500 °C, the samples were characterized by XRD, DTA, TEM and nitrogen adsorption-desorption isotherm. The use of the zirconium nitrate leads to materials having higher surface areas and narrow pore size distributions in the range of mesoporous materials; however, the preferential formation of the zirconia in the metaestable tetragonal phase was identified as the effect of the particle size allowed by the preparation method rather than the effect of the precursor. It was also found that the Mn and surfactant addition enhances the stabilization of the tetragonal crystalline phase and porosity.