Understanding the Role of Mono and Ternary Alkali Metal Salts on CO 2 Uptake of MgO Sorbents.

CO 2 uptake by MgO-based sorbents at intermediate temperatures is attractive for pre- and post-combustion CO 2 capture applications. However, besides the high CO 2 uptake potential of these materials (1.1 g CO 2 g -1 sorbent), in practice, the realistic CO 2 capture is far from that of the theorical values. In this work, the sol-gel method was used to synthetize unsupported and supported MgO sorbents (10% Ca - or 10% Ce - support, mol) that were impregnated with different fractions (15, 25, and 35; % mol) of a NaNO 3 single salt or a ternary alkali salt (NaNO 3 , LiNO 3 and KNO 3 (18/30/52; % mol)). To understand the role of alkali metal salts (AMSs) in the MgO sorbents' performance, the working and decomposition temperature ranges of AMS under different atmospheres (CO 2 and air) were evaluated. The findings show that the CO 2 uptake temperature range and maximum uptake (20-500 °C, CO 2 atmosphere) of sorbents are correlated. The cyclic CO 2 uptake of the most promising sorbents was tested along five carbonation-calcination cycles. For the first and fifth cycles, respectively, the 15 (Na, K, Li)-MgO sorbents showed the highest carrying capacity, i.e., 460-330 mg CO 2 g -1 sorbent, while for the 15 (Na, K, Li)-MgO-Ca sorbents, it was 375-275 mg CO 2 g -1 . However, after the first cycle, the carbonation occurred faster for the 15 (Na, K, Li)-MgO-Ca sorbents, meaning that it can be a path to overpassing carbonation kinetics limitations of the MgO sorbent, making it viable for industrial applications.