Effects of alkali-metal carbonates and nitrates on the CO2 sorption and regeneration of MgO-based sorbents at intermediate temperatures

Abstract

The effects of alkali-metal carbonates and nitrates on the CO2 sorption and regeneration of MgO-based sorbents were investigated in the presence of 10 vol% CO2 and 10 vol% H2O in an intermediate temperature range, 300 to 450 °C. The CO2 capture capacities of the MgO-based sorbents promoted with Na2CO3 and K2CO3 were 9.7 and 45.0 mg CO2/g sorbent, respectively. On the other hand, a MgO-based sorbent promoted with both Na2CO3 and NaNO3 exhibited the highest CO2 capture capacity of 97.4mg CO2/g sorbent at 200 °C in 10 vol% CO2, which was almost ten-times greater than that of the MgO-based sorbent promoted with Na2CO3. The CO2 sorption rate of these sorbents was higher than that of the MgO-based sorbents promoted with alkali-metal nitrates due to the formation of Na2Mg(CO3)2 or K2Mg(CO3)2 by the alkali-metal carbonate and the eutectic reaction of the alkali-metal nitrates. In addition, the reproducibility problem of double-salt sorbents obtained by the precipitation method was completely resolved by impregnating MgO with alkali-metal carbonates and nitrates. Furthermore, we found that their desorption temperatures are lower than those of the MgO-based sorbents promoted with alkali-metal carbonates due to the eutectic reaction during the regeneration process.