Synthesis of Zr-Incorporated SBA-15 Mesoporous Materials in a Self-generated Acidic Environment

Abstract

An environmentally friendly process of synthesizing Zr-incorporated mesoporous SBA-15 silica materials with the Zr content up to 0.1 Zr/Si atomic ratio and of well-ordered pore structure, high surface area, and narrow pore-size distribution was developed, where no addition of mineral acids was necessary. The main strategy of this method was to utilize the acidity self-generated in the aqueous solutions of the zirconium precursors as the catalyst for TEOS hydrolysis. In addition, the zirconium precursors also contributed to salt effect in increasing the ordering of the mesostructure. SBA-15 materials of highly ordered pores were obtained without the addition of mineral acids when the Zr/Si ratios were around 0.05. For those with the Zr/Si ratios smaller or greater than this value, the introduction of some salts, such as NaCl, in the synthesis gel was found essential in order to obtain mesostructure of high ordering and narrow pore size distribution. The amount of Zr incorporated in SBA-15 synthesized under such a mild condition was greater than that synthesized in a strong acidic environment. Moreover, the Zr content, up to Zr/Si ratio of 0.1, was close to that started with in the gel. The morphology of the Zr−SBA-15 material was found to vary with the acidity of the synthesis gels. Rodlike shape morphology was observed when no mineral acids were used, in contrast to the hexagonal platelet morphology for the material synthesized in a strong acidic environment.