Catalytic combustion study of soot on Ce0.7Zr0.3O2 solid solution

The Ce0.7Zr0.3O2 solid solution and CeO2 were prepared using the sol-gel method. The phase structure, crystallite sizes and the reducibility of the catalysts were characterized by XRD and H2-TPR techniques. XRD results indicated that Zr4 had replaced part of Ce4 to form a fluorite-like solid solution, which was favorable to obtain ultrafine nanoparticles. The ratio of main H2 consumption for Ce0.7Zr0.3O2:CeO2 was 4.4:1.0, implying that the solid solution could improve the reducibility compared to the single CeO2. The Ce0.7Zr0.3O2 solid solution catalyst showed a sharp combustion peak at 397 oC, which was 200 oC lower than that of the single soot. The good catalytic activity of the Ce0.7Zr0.3O2 was attributed to the formation of nano-CeO2-based solid solution, which enhanced the reducibility and then improved the combustion activity. As Ce0.7Zr0.3O2 could be easily reduced to Ce0.7Zr0.3O2-x, meanwhile, after oxygenation, the Ce0.7Zr0.3O2-x was recovered to Ce0.7Zr0.3O2 completely. A catalytic combustion reaction mechanism was proposed: the Ce0.7Zr0.3O2 was reduced to Ce0.7Zr0.3O2-x by the reaction with carbon and then it was recovered to Ce0.7Zr0.3O2-x by the interaction with O2.