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 degrees 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 similar to 88% and similar to 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 degrees C).