Key properties of mixed cerium and zirconium microspheres prepared by the internal gelation process with previously boiled HMTA and urea

The internal gelation process using previously boiled hexamethylenetetramine-urea was used in exploratory study to produce CeO₂–ZrO₂ microspheres, which can serve as a simulant for ceramic transuranic fuel particles and as a viable three-way catalyst. The calcined CeO₂ and ZrO₂ microspheres with Barrett–Joyner–Halenda (BJH) pore size and volumes of 8–10 nm and 0.19–0.20 mL/g, respectively, had many more surface cracks than their relatively smooth CeO₂–ZrO₂ counterparts even though the BJH pore sizes and volumes of mixed oxide spheres were lower at 3 nm and 0.11–0.12 mL/g, respectively. The Brunauer–Emmett–Teller (BET) surface areas for the CeO₂ and ZrO₂ microspheres were 74 and 93 m²/g, respectively, and the BET surface areas for the mixed oxides were much greater at 155–158 m²/g, which should improve catalytic performance. The catalytic activity of each microsphere composition was confirmed through the oxidation of carbon monoxide.