Influence of water on high-temperature CO2 capture using layered double hydroxide derivatives

Mg-Al-CO3 layered double hydroxide (LDH) was synthesized, and its thermal evolution was investigated using X-ray diffraction FTIR techniques. These patterns revealed the phase transformation of crystalline LDH to a nearly amorphous layered double oxide (LDO). LDOs derived after calcination at 400 degrees C showed good sorption potential for CO2, especially in the context of high-temperature CO2 separation from flue gases. Presence of water in the feed proved to have a positive effect as CO2 sorption increased from 2.72% (0.61 mmol/g) to 3.14% (0.71 mmol/g) tested at dry- and wet-gas conditions, respectively. CO2 sorption studies conducted using wet mixed gas (14% CO2) have also shown high sorption capacity even though CO2 concentration was diluted by almost seven times. Temperature cycling in wet conditions demonstrated high levels (75%) of desorption, which reached an equilibrium value (67%) after initial stabilization. Shorter time cycles (10 min). were found to be more effective in improving the overall efficiency of the process. Regeneration of the LDOs at 400 degrees C retrieved more than 90% of the original sorption capacity.