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

Mesoporous MgO center dot KNO3 composites were developed using an aerogel method for CO2 sorption in the intermediate temperature range of 250-400 degrees 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 13.9 wt% at 325 degrees C and 120 min, showing about 70% of the total sorption capacity within 10 min and about 7 times higher sorption capacity than pure MgO. In addition, the developed MgO center dot 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 center dot KNO3 composite during the initial 30 min was on the order of 10(-4)/s. Sorption working capacity was evaluated by 12 cyclic tests at 325 and 375 degrees C for sorption (20 min) and 450 degrees C for regeneration (30 min). Sorption working capacity was higher at 325 degrees C than at 375 degrees C, but MgO/KNO3 was highly stable at 375 degrees C, showing 90 wt% of the first cycle. (C) 2014 Elsevier B.V. All rights reserved.