Effects of preparation method on cyclic stability and CO2 absorption capacity of synthetic CaO–MgO absorbent for sorption-enhanced hydrogen production

A novel and economical method for preparing CaO-based high-temperature CO2 absorbents for sorption-enhanced hydrogen production is introduced. CaO–MgO absorbents prepared by the co-precipitation method show excellent cyclic stability but poor absorption capacity (∼8–14 g CO2/100 g absorbent). An additional hydration process provided spacious CO2 pathways resulting in a significant increase of the absorption capacity (∼17.4–47.8 g CO2/100 g absorbent) with excellent cyclic stability. As the MgO content increased, the absorption ratio of the absorbent and the degree of CaO conversion also increased. In addition, XRD analysis revealed that the hydration process followed by calcination at 900 °C led to the formation of a partial solid solution in the CaO–MgO absorbent containing 25 wt% MgO.

► Pore formation mechanism in rigid absorbent by carbonation was found.
► Co-precipitation with hydration provides excellent cyclic stability for CO2 sorbent.
► Co-precipitation with hydration also provides excellent CO2 absorption capacity.
► Uniform dispersion of MgO in CaO results in formation of solid solution.