Syntheses of mesoporous zirconia with anionic surfactants

Abstract

Synthesis of mesoporous zirconia has been performed by slowly hydrolyzing zirconium propoxide in the presence of anionic surfactants: dodecyl phosphate or sulfate (P₁₂ and Sf₁₂) and hexadecyl sulfonate (So₁₆). t-Plot surface areas >400 m² g^–1 and diffraction lines corresponding to spacings near 45 Å were measured for solids outgassed at 140–150 °C. This treatment does not remove the surfactant. After calcination in air at 500 °C and combustion of the surfactant the spacing increases to ca. 70 Å and the mesoporous volume is reduced by a factor of about 2, whereas the pore wall material crystallizes in the tetragonal phase. A schematic model in which the surfactant is a scaffold component is suggested in order to explain these results. It is very different from the templating mechanisms reported for zirconia by others. The high resolution electron microscopic study reveals the presence of a disorganized network of polygonal pores in the solids obtained through the mediation of surfactant. It is suggested that the chemistry of the hydrolysis solution is instrumental in the organization of the pore structure and in determining the thickness of the walls. In agreement with others, the fixation of PO₄ or SO₄ in the walls may help to preserve the porous structure.