Absorption and release of carbon dioxide with various metal oxides and hydroxides

Abstract

Lithium silicate (Li 4SiO 4) and lithium zirconate (Li 2Zr0.i) absorb CO 2 in a lower temperature range and the absorbed CO 2 is released reversibly in a higher temperature region. In this study, various metal oxides and hydroxides and their complex oxides containing Li were investigated for their CO 2 absorption properties at different temperatures in order to get better understanding of the related mechanism. The inflection points in the TG curves, at which predominant reaction changes from CO 2 absorption to CO 2 release, are observed at around 973 K for Li 4SiO 4 and Li 2ZrO 3. The CO 2 absorption is based on the formation of Li 2CO 3 through the decomposition of Li-containing complex oxides. From the experimental results and thermodynamical calculations, it is noticed that CO 2 absorption takes place very slowly in spite of large equilibrium constant in the lower temperature region below 873 K, while the absorption at 973 K happens quickly. When the absorption at 973 K and the release at 1273 K are repeated 5 times for Li 4SiO 4, the material maintains its crystal structure to give CO 2 absorption and release. On the other hand, CaO shows an inflection point at 1173 K in the TG curve. Magnesium oxide and hydroxide do not react with CO 2 below 1273K. © 2007 The Mining and Materials Processing Institute of Japan.