The role of potassium in K/Co3O4 for soot combustion under loose contact

This work investigated the effect of potassium (K) on the catalytic activity of Co3O4 prepared by sol-gel method for soot combustion under loose contact. The catalysts were characterized by XRD, TPR, Raman, FT-IR, and XPS. The results showed the deposition of 4.4 wt.% K accelerated the activity of Co3O4 for soot combustion under loose contact, the temperature of maximum soot oxidation rate (Tm) decreased from 490 degrees C over Co3O4 to 417 degrees C over K(0.1)/Co3O4(600). It was discovered that there is an exact linear relationship between Tm and the value of active Co3+/Co for the first time, where Co represented the total amount Co3+ and Co2+. Our findings strongly suggested that potassium, as a promoter, not only favors CB-catalyst contact, but also produces more active Co3+ with the increase of K content. Doped K entered the crystal lattice and aroused the lattice distortion. The Tm in TPO decreased linearly with the increase of microstrain. The lattice distortion and the interaction of K and Co3O4 promoted the formation of the surface active Co3+ and active O-, and improved the activity of lattice oxygen. (C) 2011 Elsevier B.V. All rights reserved.