MgO-Based Composites for High Pressure CO2 Capture: A First-Principles Theoretical and Experimental Investigation

Magnesium oxide (MgO) is an interesting material with tunable acido-basic properties. MgO-based composite sorbents (MgAl 2 O 4 , MgSiO 3 , and MgTiO 3 ) have drawn much attention based on their high temperature CO 2 sorption. In this study, the theoretical and experimental investigation by phonon calculations and high-pressure CO 2 sorption were conducted to identify a potential candidate to achieve CO 2 capture under pre-combustion conditions. The divergence of the physico-chemical properties of the various sample materials was found to be the determining factor for the enhanced CO 2 sorption. From the high-pressure CO 2 sorption experiment at 200 o C, MgAl 2 O 4 shows high chemisorption capacity of CO 2 compared to the other systems such as MgO, MgSiO 3, and MgTiO 3 . However, the thermodynamic properties of MgAl 2 O 4 for CO 2 capture were found to be less favorable than those of other compounds in our phonon calculations. In other words, the carbonation of MgAl 2 O 4 , producing MgCO 3 is not a favorable reaction at the experimental condition in our phonon calculations due to the formation of Al 2 O 3 as a byproduct. On the other hand, MgO was experimentally found to have low adsorption capacity under similar conditions. Contrarily, the carbonation of MgO, which has a large number of basic sites at pre-combustion conditions and produces MgCO 3 , is found to be favorable in our calculations clearly defining the existence of tradeoff properties under practical CO 2 sorption conditions.