Ceria–zirconia mixed oxide prepared by continuous hydrothermal synthesis in supercritical water as catalyst support

A number of different synthetic methods have been applied to prepare ceria–zirconia and related mixed oxides. Continuous hydrothermal synthesis in supercritical water (supercritical synthesis) is a method to prepare metal oxide nanoparticles rapidly and continuously using supercritical water as anti-solvent. Highly crystallized nanoparticles of homogeneous complex metal oxides as well as single metal oxides could be produced easily by the supercritical synthesis. It would be valuable to compare the physicochemical properties of ceria–zirconia mixed oxides prepared by the supercritical synthesis and those by other conventional methods.The supercritical synthesis could lead to ceria–zirconia mixed oxides with higher thermal stability and better oxygen storage capacity (OSC) due to its sparsely-agglomerated morphology, while the co-precipitation resulted in densely agglomerated morphology. Rh-loaded ceria–zirconia catalysts with ceria–zirconia as support were applied for catalytic reduction of NO by CO. Rh-loaded ceria–zirconia catalyst by supercritical synthesis showed superior catalytic performances, together with better reducibility and higher thermal stability. Ceria–zirconia mixed oxide prepared by supercritical synthesis had more potential applications as catalyst support mainly due to its sparsely-agglomerated morphology and higher thermal stability, compared with those by the co-precipitation method.

Schematic diagram for the changes in the morphologies of ceria–zirconia mixed oxides prepared by (a) supercritical synthesis and (b) co-precipitation method.Figure optionsDownload high-quality image (189 K)Download as PowerPoint slideHighlights
► Continuous hydrothermal synthesis in supercritical water for the preparation of metal oxide nanoparticles with sparsely-agglomerated morphology.
► Ceria–zirconia mixed oxide with high thermal stability and large oxygen storage capacity even after redox-aging at 1000 °C.
► Rh-loaded catalyst with ceria–zirconia as support for the reaction between NO and CO.