The influence of mechanical treatment on the absorption of CO2 by perovskite oxides

Perovskite oxides of composition (Sr1-xCax)(Fe0.5Co0.5)O3-delta were investigated for CO2 absorption properties and were proved to be useful as materials for CO2 absorption in the temperature range from 550 to 850 degreesC. The absorption rate of CO2 increased with Ca doping. The mechanical treatment of perovskite oxides for several minutes, especially for the oxides containing a small amount of Ca, was found to be effective for activating the oxides for CO2 absorption and for reducing the starting temperature of CO2 absorption by about 80 degreesC. However, it was not less effective to treat the oxides for a long time. The site distortion due to Sr and Ca ions at site A and the mixed valence states at site B were confirmed to be effective for CO2 absorption at high temperatures. During the absorption of CO2, a spinel compound was formed according to the following reaction: 2(Sr,Ca)(Fe,Co)O-2.5 + CO2 --> (Sr,Ca)CO3 + (Sr,Ca)(Fe,Co)(2)O-4.