Influence of Water on High-Temperature CO₂ Capture Using Layered Double Hydroxide Derivatives

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Mg−Al−CO 3 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 °C showed good sorption potential for CO 2, especially in the context of high-temperature CO 2 separation from flue gases. Presence of water in the feed proved to have a positive effect as CO 2 sorption increased from 2.72% (0.61 mmol/g) to 3.14% (0.71 mmol/g) tested at dry- and wet-gas conditions, respectively. CO 2 sorption studies conducted using wet mixed gas (14% CO 2 ) have also shown high sorption capacity even though CO 2 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 °C retrieved more than 90% of the original sorption capacity.