High-Surface-Area SiO2–ZrO2 Prepared by Depositing Silica on Zirconia in Aqueous Ammonia Solution

Preparation of high-surface-area SiO2–ZrO2 by deposition of silicate species on zirconia under hydrothermal conditions in an aqueous ammonia solution was investigated. A fresh precipitate of ZrO(OH)2 was heated in a pressure vessel with several pieces of quartz glass tube at 100°C. In the measurement of ICP-AES and solid-state 29Si NMR, it was elucidated that a silica component dissolved from the glass in the basic solution was deposited on the ZrO(OH)2 precipitate and that the silica content increased with increasing hydrothermal period. The resulting SiO2–ZrO2 had a specific surface area higher than 240 m2 g−1 even after calcination at 500°C. In contrast to the pure ZrO2 particles readily aggregating, the silicate species deposited on the surface of ZrO2 particles prevented the agglomeration of the primary particles during calcination, resulting in high-surface-area SiO2–ZrO2.