A complex and de-complex strategy to ordered mesoporous Ce0.5Zr0.5O2 with comprehensive pilot scale performances

Abstract

Synthesis of ordered mesoporous ceria-zirconia (CeO2–ZrO2, M-CZ) solid solution in water-based conditions have challenged scientists for a long time due to the extremely different chemical properties of cerium and zirconium cations. This study discuss the synthesis of highly ordered mesoporous Ce0.5Zr0.5O2 solid solution in aqueous solution through a new complex and de-complex method using di-cationic Gemini as the template. The method takes advantage of the coordinative capability of citric acid (CA) to allow the coexistence of inorganic resources in mild basic solutions and uses the strong oxidic capability of H2O2 to precipitate Ce and Zr cations homogeneously. Through this strategy, the combination between inorganic–organic groups in aqueous solution was avoided, whereas coordination between inorganic–organic species was realized. Mechanisms show that the formation of peroxycarboxylic groups (–COOOH) from the reaction between metal-CA molecular and hydroxyl radical (OH) was the key process. Meso-scale micelles were formed during hydrothermal treatment, while hexagonally arranged pores with narrow size distribution were obtained in the calcination procedure. The surface area of the calcined product was 228 m2 g−1 with a pore volume of 0.7 cm3 g−1, whereas oxygen storage capacity was 652 μmol g−1. The M-CZ product illustrated fairly good pilot-scale three-way catalytic (TWC) performances thanks to the thin pore walls in the mesostructures. A complete (100%) conversion of CO and NOy at 340 °C was detected in the engine pedestal tests. The complex and de-complex strategy may provide a new route for the preparation of ordered mesoporous composite oxides.