Optimising the acid-base ratio of Mg-Al layered double oxides to enhance CO2 capture performance: the critical role of calcination conditions.

Abstract

The effect of calcination conditions (ramp rate, calcination temperature and time) on the formation of Mg2Al layered double oxides (Mg2Al LDOs) as well as their CO2 capture performance, has been systematically investigated. This study explores novel insights into the intricate relationship between these calcination conditions and the resulting surface characteristics, which play a vital role in CO2 capture efficiency. Notably, it is revealed that a rapid ramp rate (100 °C min-1) significantly increases surface area and hydroxyl concentration, leading to a 69% increase in CO2 capture efficiency compared to slower ramp rate. Conversely, short calcination times (1 h) and fast ramp rates (100 °C min-1) are observed to compromise CO2 adsorption due to the presence of dehydrated LDHs. A critical acid : base ratio of 0.37, achieved from a fast ramp rate (100 °C min-1) at 400 °C for 2 h, was found as a key threshold for optimising surface properties, effectively balancing favourable hydroxyl and less favourable strong acid sites, thereby maximizing CO2 capture performance.