In the present work, K/La2O3 was prepared and tested as a potential catalyst to be used in a diesel engine exhaust. The soot combustion activity was evaluated by temperature-programmed-oxidation (TPO), and the NOx-catalyst interaction was studied using a microbalance experiment. The SO2 poisoning process and the regeneration of a poisoned K/La2O3 catalyst were analyzed. The fresh catalyst presented a good soot combustion activity. After being treated with a 1000 ppm SO2 stream, the catalyst was poisoned due to lanthanum sulfate and potassium sulfate formation. The NOx treatment contributed to the K-2(SO4) decomposition at the expense of extra La-2(SO4)(3) formation and the H-2 treatment contributed to the La-2(SO4)(3) decomposition.(c) 2007 Elsevier B.V. All rights reserved.