Facile synthesis of hierarchically porous MgO sorbent doped with CaCO3 for fast CO2 capture in rapid intermediate temperature swing sorption

For CO2 sorbents, a fast sorption rate is as important as the sorption capacity in order to enable efficient CO2 capture in the treatment of large amounts of emission gas, where the contact time between the sorbent and gas is limited. A facile and environmentally benign method of fabricating advanced sorbents with fast CO2 sorption for pre-combustion capture was developed by incorporating CaCO3 into triple salt-promoted MgO sorbents (LiNO3, NaNO3, and Na2CO3) using salt-controllable coprecipitation. The incorporation of Ca into the salt-promoted MgO (MgCa) was effective for controlling the lattice parameter, textural properties, and basicity. The salt-promoted MgCa sorbents had a bi-disperse pore distribution with different range, which contributed to the fast sorption. When 5 mol.% of Ca was doped into the triple salt-promoted MgO, the CO2 sorption capacity within 10 min was significantly improved (from 6 wt% (MgO) to 43 wt% (MgCa-5%)) at 325 degrees C. For CO2 sorption for 10 min at 325 degrees C and N-2 regeneration for 5 min at 400 degrees C, the working capacity of MgCa-5% was approximately 30 wt% at the 30 th cycle. Under the same rapid cycling conditions, the sorption capacity was 12 wt% when a wet CO2 mixture (29 vol% CO2, 3 vol% H2O, and balance N-2) and pure CO2 was used for sorption and regeneration, respectively. When the regeneration gas contained water vapour, the cyclic sorption capacity decreased to 1-2 wt%. The MgCa sorbents prepared via salt-controllable coprecipitation exhibited high working capacities during the rapid cyclic temperature swing operation at intermediate temperature.