Deactivation of Co,K catalysts during catalytic combustion of diesel soot: Influence of the support

CARLOS QUERINI, FABIÁN RAVELLI, MARÍA ALICIA ULLA, LAURA CORNAGLIA, EDUARDO MIRÓ

STUDIES IN SURFACE SCIENCE AND CATALYSIS

Elsevier

Año: 1999 vol. 126 p. 257 - 264

0039-3037

The thermal deactivation of catalysts containing 12wt.% of Co and 4.5 or 7.5 wt.% of Ksupported on MgO, CeO2 and La203 has been studied for the diesel soot catalytic combustion.It has been found that this reaction occurs by a redox mechanism on any of the abovementioned supports. While on MgO and La203 supported catalysts Cobalt oxide species areresponsible for the supply of oxygen during the redox reaction, on CeO2 as support, the Codoes not improve the activity of the K/CeO2, since in this case the support itself displaysredox properties. It has been found that the thermal deactivation mechanism strongly depends on the support. When MgO is used, the formation of a solid solution (Co,Mg) with low redox capacity is responsible for deactivation. The presence of 7.5% of K avoids the formation of the said solid solution thus preserving the activity. In the case of CeO2, during high calcination temperatures a blockage of part of the support with potassium occurs, which leads to a decrease in the redox property of the catalyst and, consequently, to a loss of activity.La203 supported catalysts lose activity due to the formation of a mixed oxide with aperovskite structure (LaCoO3) with lower redox capacity than cobalt oxide supported species.