Effect of Dual Templates On Texture Properties of Mesoporous Alumina Prepared by Spray Pyrolysis

ABSTRACT

Porous alumina is one of important engineering materials due to its catalytic, electronic, and biomedical properties. Mostly, mesoporous alumina has been synthesized by a liquid-phase reaction method using surfactant micelles or organic additives as structure-directing agents. In most applications, the mesoporous alumina should have a high surface area, well-defined pore structure, and a narrow pore size distribution. So, many researchers have been devoted to synthesize high porous alumina with regularity in pore size. Recently, an aerosol route using spray-drying and self-assembly was reported as a potential method to prepare mesoporous particles with high surface area. Most of researches using the aerosol route are focusing on silica or metal/silica.

In this work, a conventional spray pyrolysis process was applied to prepare mesoporous alumina particles with spherical shape. In special, various dual templates such as CTAB, CTAC, P123, CTAB/P123, and CTAC/P123 were used to investigate the changes in the texture properties of alumina. Fig.1 shows nitrogen-adsorption–desorption isotherms of alumina particles prepared by the spray pyrolysis with the CTAB and CTAB/P123 mixture as a template. The prepared alumina shows a typical type IV isotherm. The BET surface area of the alumina prepared by using only CTAB was 233 m²/g. Also, the sample prepared from the dual template, CTAB/P123, had the BET surface area of 282 m²/g. In terms of pore size and pore volume, however, the alumina particles prepared from the dual template (CTAB/P123) were larger than the alumina prepared from using the only CTAB template. On the base of BJH desorption isotherms, the pore size distribution was calculated and shown in Fig. 1. When the only CTAB was used, a broad pore size distribution was observed compared with that for the alumina sample prepared from the CTAB/P123 dual template. From this result, it was clear that using the dual template is helpful to improve the pore properties of alumina particles when they are prepared by the spray pyrolysis. The TEM images of the mesoporous alumina prepared using the CTAB/P1223 template were shown in Fig. 2. Also, the SAXS result was inserted in Fig. 2. The prepared particles have spherical morphology and a clear SAXS peak indicating the presence of mesopores with a uniform size which can be confirmed by the TEM image. As the same vein, we investigated the effect of different dual templates such as CTAC/P123 on the texture properties. More details in analysis and discussion will be presented.