Carbonation Characteristics of Dry Sodium-Based Sorbents for CO2Capture

Na 2 CO 3 is one potential capture medium with the potential to decrease CO 2 emission. Carbonation characteristics of four sodium-based sorbents were studied using thermogravimetric analysis (TGA), X-ray diffraction, scanning electron microscopy, and nitrogen adsorption apparatuses. Results show that, in TGA tests (carbonation atmosphere of 15% CO 2 + 15% H 2 O(g) + 70% N 2 and carbonation temperature of 333 K), sorbent Na 2 CO 3 [analytical reagent (AR)] is impervious, while sorbent Na 2 CO 3 calcined from NaHCO 3 (AR) reacts, mostly forming Na 5 H 3 (CO 3 ) 4 instead of NaHCO 3, corresponding to 72.87% conversion of Na 2 CO 3 in about 140 min. With regard to the TGA tests of sorbent Na 2 CO 3 /Al 2 O 3 and sorbent Na 2 CO 3 /Al 2 O 3 calcined from NaHCO 3 /Al 2 O 3, only NaHCO 3 is generated and the carbonation conversions are both above 85% in about 55 min. The microstructure changes were observed to analyze the reaction mechanisms and carbonation characteristics. It is confirmed that, by loading active components on Al 2 O 3, the microscopic structures can be significantly improved, contributing to the great improvement of carbonation characteristics of the latter two sorbents. On the other hand, there is little improvement of carbonation characteristics using NaHCO 3 as precursors for sorbents supported on Al 2 O 3 .