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

C. A. QUERINI; F. RAVELLI; M. A. ULLA; L. M. CORNAGLIA; E. E. MIRÓ

STUDIES IN SURFACE SCIENCE AND CATALYSIS

Elsevier B.V.

Lugar: Amsterdam; Año: 1999 vol. 126 p. 257 - 264

0167-2991

The thermal deactivation of catalysts containing 12wt.% of Co and 4.5 or 7.5 wt.% of K supported on MgO, CeO2 and La2O3 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 above mentioned supports. While on MgO and La2O3 supported catalysts Cobalt oxide species are responsible for the supply of oxygen during the redox reaction, on CeO2 as support, the Co does not improve the activity of the K/CeO2, since in this case the support itself displays redox 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. LaiOs supported catalysts lose activity due to the formation of a mixed oxide with a perovskite structure (LaCoO3) with lower redox capacity than cobalt oxide supporte species