Mesoporous MgO sorbent promoted with KNO3 for CO2 capture at intermediate temperatures

Mesoporous MgO�KNO3 composites were developed using an aerogel method for CO2 sorption in the intermediate temperature range of 250-400�C. The effects of MgO/KNO3 molar ratio, calcination method and sorption temperature on CO2 sorption rate and capacity were evaluated using a thermogravimetric analyzer. The composite prepared at a MgO/KNO3 molar ratio of 1:0.2 with a four-step calcination had the high CO2 sorption capacity of 13.9wt% at 325�C and 120min, showing about 70% of the total sorption capacity within 10min and about 7 times higher sorption capacity than pure MgO. In addition, the developed MgO�KNO3 composite showed higher sorption capacity than other MgO composites promoted by alkali metal salts (K2CO3, KOH, NaNO3, Na2CO3, Na2HPO4, LiNO3 and Li2CO3). The sorption rate of CO2 on a MgO�KNO3 composite during the initial 30min was on the order of 10-4/s. Sorption working capacity was evaluated by 12 cyclic tests at 325 and 375�C for sorption (20min) and 450�C for regeneration (30min). Sorption working capacity was higher at 325�C than at 375�C, but MgO/KNO3 was highly stable at 375�C, showing 90wt% of the first cycle. � 2014 Elsevier B.V.