Effects of calcination temperature and atmosphere on the CO2 sorption and regeneration characteristics of potassium-based sorbents using ZrO2 or TiO2 as supports were investigated in a fixed bed reactor in a temperature range 60-150 degrees C. We found in this study that potassium-based sorbents using ZrO2 showed excellent CO2 capture capacity regardless of calcination temperature and atmosphere. This is due to the fact that the potassium-based ZrO2 sorbents form only K2CO3 and ZrO2 phases without any new alloy species, whereas the inactive K-Ti alloy species such as K2Ti2O5 and K2Ti6O13 are formed during calcination for potassium-based sorbents using TiO2. From these results, we conclude that the thermal stability of the sorbents can be improved by using ZrO2 as a support instead of TiO2. (C) 2013 Elsevier Ltd. All rights reserved.