Carbonation behavior of K2CO3/AC in low reaction temperature and CO2 concentration

• K2CO3/AC provides a new choice for CO2 removal in confined space.
• The reaction path of K2CO3/AC consists of two steps as hydration and carbonation.
• The adsorption process exists in the CO2 removal process of K2CO3/AC.
• The effect of the CO2 concentration is not significant on CO2 removal of K2CO3/AC.
• The Relative Humidity plays an important role in the CO2 removal process of K2CO3/AC.

K2CO3 loaded on activated carbon (K2CO3/AC) was thought to be a proper sorbent with a high CO2 sorption capacity for CO2 removal in confined spaces. However, the carbonation reaction mechanism of K2CO3/AC in low temperature and low CO2 concentration is not clear. In this work, the carbonation behavior of K2CO3/AC was investigated in the condition of low reaction temperatures of 20–60 °C and low CO2 concentrations of 0–4% in TGA. The reaction path of K2CO3/AC consists of two steps as that the hydration reaction occurs first to form K2CO3·1.5H2O and K4H2(CO3)3·1.5H2O, then KHCO3 is produced rapidly. Besides the carbonation reaction, the adsorption process exists either. More K2CO3 will be converted to KHCO3 for the sorbent with low K2CO3 loadings or in the conditions of high reaction temperature and low H2O concentration. More K4H2(CO3)3·1.5H2O and K2CO3·1.5H2O will be formed for the sorbent with high K2CO3 loadings or in the conditions of low reaction temperature and high H2O concentration. The effect of the CO2 concentration is not significant on the carbonation reaction paths of K2CO3/AC. On the contrary, the Relative Humidity (RH) plays an important role in this process.