Cobalt deposited on micro and nanometric structures of ceria and zirconia applied in diesel soot combustion

Abstract

Two series of shaped catalysts were obtained, one of them from CeO2 and the other one from ZrO2, to which cobalt was added. On the one hand, ceria fibers prepared by electrospinning exhibited greater catalytic activity for soot combustion, under loose contact and in the presence of NO, than those made by hydrothermal synthesis. The deposition of low loads of cobalt (2 wt.%) resulted in a positive effect for soot combustion (maximum soot combustion rate, TM = 360 °C), whereas higher loadings (12 wt.%) did not result in a further improvement. On the other hand, cobalt catalysts supported on zirconia nanorods were prepared by hydrothermal synthesis. In comparison with the ceria catalysts, zirconia showed a better catalytic activity when the cobalt load increased from 2 to 12 wt.%, due to a better dispersion of cobalt on ZrO2. This is in line with STEM and EDX results that indicated the presence of smaller aggregates of cobalt on the zirconia surface. Among the ZrO2 catalysts studied, Co(12%)-ZrO2 presented the best catalytic activity (TM = 360 °C), obtained under loose contact conditions and in the presence of NO. The activity of the catalysts was thoroughly correlated with the characterization of the samples by XRD, SEM, EDX, STEM, LRS and XPS.