Synthesis of LiAl2-layered double hydroxides for CO2 capture over a wide temperature range

Abstract

Although there are many reports on layered double hydroxide (LDH) derived CO₂ adsorbents, none of them have studied the special case of LiAl₂ LDHs. Here we report the first detailed investigation of the performance of LiAl₂ LDHs as novel CO₂ adsorbents. LiAl₂ LDHs were synthesized using both traditional coprecipitation and gibbsite intercalation methods. All the materials were thoroughly characterized using XRD, SEM, TEM, FTIR, BET, and TGA. The CO₂ capture performance of these LDHs were investigated as a function of charge compensating anions, Li/Al ratio in preparation solution, calcination temperature, adsorption temperature, and doping with K₂CO₃. The data indicated that LiAl₂ LDHs derived compounds can be used as CO₂ adsorbents over a wide temperature range (60–400 °C), with a CO₂ capture capacity of 0.94 and 0.51 mmol g⁻¹ at 60 and 200 °C, respectively. By doping LiAl₂–CO₃ LDH with 20 wt% K₂CO₃, the CO₂ adsorption capacity was increased up to 1.27 and 0.83 mmol g⁻¹ at 60 and 200 °C, respectively. CO₂ adsorption–desorption cycling studies showed that both pure LiAl₂ LDH and the K₂CO₃-promoted LiAl₂ LDH had stable CO₂ capture performance even after 22 cycles. Considering its high CO₂ capture capacity and good cycling stability, LiAl₂ LDH based novel CO₂ adsorbents have significant potential for CO₂ capture applications.