Synthesis of bimodal mesoporous titania with high thermal stability via replication of citric acid-templated mesoporous silica

Abstract

We first synthesized the mesoporous titania, designated KRICT-MT, via replication of the citric acid (CA)-templated mesoporous silica, composed of the silica-nanosphere framework. The KRICT-MT showed the extremely high thermal stability and bimodal mesostructure with the small primary mesopores of 4-5 nm and the large secondary mesopores of 50 nm in mean pore diameter, which are three-dimensionally interconnected. In general, the anatase is transformed into the rutile by thermal treatment in the temperature range of 600-800°C, and the mesostructure of the mesoporous titania is collapsed above 600°C along with a significant decrease in pore properties such as specific surface area and pore volume. In contrast, the anatase-rutile phase transformation of the KRICT-MT was not observed up to 900°C, resulting in the maintenance of its high pore properties at high temperature. In addition, we employed the KRICT-MT as a catalyst support for water-gas shift reaction. The Pt-impregnated KRICT-MT showed much higher catalytic activity than the Pt-impregnated Degussa P25. The remarkably high catalytic activity of the Pt/KRICT-MT is attributed to the three-dimensionally interconnected and bimodal mesostructure. © 2007 American Chemical Society.