Synthesis of tetragonal zirconia in mesoporous silica and its catalytic properties for methanol oxidative decomposition

Abstract

The synthesis of zirconia with large specific surface area by the hard template method has been conducted using KIT-6 mesoporous silica. Composite materials of tetragonal zirconia and silica were successfully synthesized by the decomposition of zirconia sources in the mesoporous space of KIT-6, while zirconia in the monoclinic and tetragonal phases was synthesized by the conventional pyrolysis method from the same zirconium sources. The formation behavior of tetragonal zirconia depends on the zirconium source, the pore size of mesoporous silica, the amount of the introduced zirconia source, and the calcination temperature. We conclude that the crystallization of zirconia in the mesoporous space results in the formation of fine zirconia particles (crystallite size effect), leading to the formation of a pure tetragonal zirconia crystal. Furthermore, the nanosized tetragonal zirconia possessing large BET specific surface area was synthesized by removing the silica component in the zirconia–silica composite with alkaline treatment. Additionally, we have evaluated the catalytic performance of tetragonal zirconia materials for methanol oxidative decomposition. Among the zirconia samples synthesized in the present study, the sample prepared by the hard template method and calcined at 800 °C exhibited the highest activity for methanol oxidation. We deduce that crystallinity of zirconia and high BET specific surface area are necessary to achieve high catalytic activity.