In order to develop highly active sorbent for COS removal, Fe-Mn mixed oxides doped with CeO(2), La(2)O(3) or Sm(2)O(3) were studied. The effects of these promoters on the structural properties of Fe-Mn oxides were investigated by XRD, BET, TPR and TEM techniques. XRD results revealed that the degree of crystallinity of Fe-Mn oxide phase decreased due to the addition of rare-earth oxides. Doping with CeO(2), La(2)O(3) or Sm(2)O(3) led to an increase in BET surface area of the sample. TPR studies showed that the reactivity of the reduction of doped samples increased in the temperature range of 300-450 degrees C. in addition, the desulfurization test was performed at 325 degrees C with a gas hourly space velocity of 1000 h(-1). It was found that the addition of 3% La(2)O(3) greatly improved the absorption sulfur capacity of the sorbent, while the sorbent doped 3% CeO(2) achieved a sufficiently high purifying degree before breakthrough. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.