High temperature adsorption of CO 2 on Mg–Al hydrotalcite: Effect of the charge compensating anions and the synthesis pH

Abstract

This work reported a detailed investigation on how charge compensating anions and synthesis pH affect the structural properties and CO 2 adsorption capacity of Mg–Al hydrotalcites (HTs). A series of Mg 3Al 1–A (A = CO 3 2−, HCO 3 −, NO 3 −, SO 4 2−, and Cl −) HTs were synthesized and tested as high temperature CO 2 adsorbents. It was found that the anions have great effect on the thermal stability and morphology, as well as on the surface area of HTs, consequently influencing the CO 2 adsorption capacity of HT derivatives. Among various HTs, Mg 3Al 1–CO 3 showed the highest CO 2 adsorption capacity of 0.53 mmol/g. Next, the influence of synthesis pH on the Mg/Al ratio, BET surface area, pore size, and CO 2 adsorption capacity of Mg 3Al 1–CO 3 was investigated. Mg 3Al 1–CO 3 synthesized at pH = 10–12 showed good performance for CO 2 adsorption. By doping Mg 3Al 1–CO 3 (pH = 10) with 20 wt.% K 2CO 3, the CO 2 adsorption capacity was increased up to 0.85 mmol/g.