Promoting effects of Li3PO4 and CaCO3 on the intermediate-temperature CO2 adsorption over molten NaNO3-promoted MgO-based sorbents

Abstract

Molten nitrate-promoted MgO-based sorbents represent a potential class of materials for CO2 capture at intermediate temperatures. However, their poor stability under harsh but realistic regeneration conditions (e.g., at high temperatures in pure CO2) is a challenge for the application of CO2 capture. In this work, a series of NaNO3 and/or Li3PO4 promoted MgO and MgO-CaCO3 sorbents were prepared, characterized, and evaluated. The results showed that the NaNO3-Li3PO4 promoted MgO-CaCO3 sorbents had high CO2 adsorption performance in terms of rate, capacity and stability, which was attributed to the promoting effect of Li3PO4 and CaCO3. Li3PO4 can enhance the surface adsorption of CO2 by providing some extra moderate basic sites, while CaCO3 can accelerate the carbonation reaction of bulk MgO via the formation of CaMg(CO3)2. In addition, Li3PO4 can hinder the sintering of sorbent particles, and consequently improve the stability of the sorbent. The optimized sorbent had a stable CO2 uptake of 0.12 (or 0.26) gCO2/gsorbent when 30% (or pure) CO2 was used at the adsorption stage in long-term cyclic operation (desorption at 500 °C in pure CO2 for both cases), showing promising applications in intermediate-temperature CO2 capture and thermochemical energy storage.