Aqueous miscible organic-layered double hydroxides with improved CO2 adsorption capacity

Abstract

Potassium-promoted layered double hydroxide (LDH)-derived materials are suitable elevated temperature CO2 adsorbents for pre-combustion CO2 capture. A challenge for the commercialization of LDHs as efficient CO2 adsorbents is their low capacities (ca. 0.5–0.6 mmol/g@400 °C) due to their hydrogen-bonded stacked structure. In this study, the aqueous miscible organic solvent treatment (AMOST) was used to exfoliate Mg3Al–CO3 LDH into nanosheets with a flower-like morphology, resulting in high surface areas of 287 and 212 m2/g for CC1 (washed with ethanol) and CC2 (washed with acetone), respectively. The exfoliated LDH structure exposed more interlayered CO2 active sites and promoters for alkali metal modification. Six impregnation solvents, water, acetone, ethanediol, ethanol, DMAC, and methanol were screened to optimize the CO2 uptake of 20 wt% K2CO3-promoted CC1. K2CO3/CC1(ed) using ethanediol as the impregnation solvent reached a CO2 working capacity of 1.46 mmol/g at 400 °C in the first cycle and 1.23 mmol/g after 10 cycles, twice the capacity of the commercial K2CO3/MG70. Material characterization indicated that the unexpectedly high performance of K2CO3/CC1(ed) could be attributed to the uniform K+ dispersion on the surface of K2CO3/CC1(ed) rather than bulk phase formation and the release of the residual solvent during calcination that could generate more paths for CO2 diffusion.