Fabrication of microporous calcite block from calcium hydroxide compact under carbon dioxide atmosphere at high temperature

Abstract

Effects of carbonation temperature and compacting pressure on basic properties of calcite block were studied using Ca(OH) 2 compact made with 0.2-2.0 MPa and their carbonation at 200-800°C for 1 h. Microporous calcite was obtained only when carbonated at 600°C using Ca(OH) 2 compact made with 0.2 MPa even though thermogravimetry analysis showed that calcite powder was stable up to 920°C under CO2 atmosphere. CaO formed by carbonation at 700°C and 800°C is thought to be caused by the limited CO2 diffusion interior to the Ca(OH) 2 compact. Also, unreacted Ca(OH) 2 was found for Ca(OH) 2 compact prepared with 0.5 MPa or higher pressure even when carbonated at 600°C. As a result of high temperature carbonation, crystallite size of the calcite, 58.0 nm, was significantly larger when compared to that of calcite prepared at room temperature, 35.5 nm. Porosity and diametral tensile strength of the microporous calcite were 39.5% and 6.4 MPa.