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, capture performance of molten salts-promoted Mg-Al-palmitate layered double oxides (LDOs) as well as an in situ DRIFT analysis to determine the CO2 sorption mechanism of these samples. The Mg-Al-palmitate layered double hydroxides (LDHs) coated with (Li-Na-K)NO3 molten salts were successfully prepared by coprecipitation and wet impregnation methods and their CO2 capture performance have been systematically tested under different high pressures and different adsorption temperatures. Results showed high and stable CO2 sorption (7-8 mmol CO2/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 CO2 sorption process at temperatures as high as 350 degrees C. Thus, CO2 is incorporated on the NO3- melted, producing NO2- and CO32-, where O- is released from the nitrate to nitrite. After that, CO32- reacts with the LDO material forming MgCO3. In that second reaction, O- is reincorporated to the nitrite, recovering the NO3- initial species.