Layered Double Hydroxides for CO2 Capture: Structure Evolution and Regeneration

Mg-Al-CO3 layered double hydroxide (LDH) was synthesized, and its thermal evolution was investigated using X-ray diffraction, FTIR spectroscopy, and thermogravimetric analysis (TGA). The resultant LDH derivatives showed excellent CO2 adsorption capabilities, especially suitable for high-temperature CO2 separation from flue gases. Calcination of crystalline LDHs at 400 °C led to phase transformation yielding amorphous Mg-Al mixed oxides having a CO2 sorption capacity of 0.49 mmol/g at 200 °C. Reversible and irreversible CO2 sorption was determined to be ~88% and ~12% of the total CO2 sorption, respectively. Regeneration restored the Mg-Al mixed oxide to 98% of its initial CO2 sorption after several cycles of CO2 adsorption testing. This clearly indicates the desirable properties of Mg-Al mixed oxide for CO2 capture from flue gases at high temperatures (up to 200 °C).