High and Efficient CO₂ Capture in Molten Nitrate-Modified Mg–Al–Palmitate Layered Double Oxides at High Pressures and Elucidation of Carbonation Mechanisms by in Situ DRIFT Spectroscopy Analysis

We report a systematic investigation on the high-pressure CO 2 capture performance of molten salts-promoted Mg–Al–palmitate layered double oxides (LDOs) as well as an in situ DRIFT analysis to determine the CO 2 sorption mechanism of these samples. The Mg–Al–palmitate layered double hydroxides (LDHs) coated with (Li–Na–K)NO 3 molten salts were successfully prepared by coprecipitation and wet impregnation methods and their CO 2 capture performance have been systematically tested under different high pressures and different adsorption temperatures. Results showed high and stable CO 2 sorption (7–8 mmol CO 2 /g) at moderate temperatures, even after 10 cycles. Complementary, an in situ DRIFT analysis evidenced that nitrate addition to LDH samples plays an important role during CO 2 sorption process at temperatures as high as 350 °C. Thus, CO 2 is incorporated on the NO 3 – melted, producing NO 2 – and CO 3 2–, where O – is released from the nitrate to nitrite. After that, CO 3 2– reacts with the LDO material forming MgCO 3 . In that second reaction, O – is reincorporated to the nitrite, recovering the NO 3 – initial species.