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Four diverse microstructured MgO-stabilized CaO sorbents with varying mixing characteristics of Ca and Mg were obtained from untreated, hydrated, precipitated, and milled dolomite. Different morphological characterizations (thermal decomposition, phase composition, morphology, and nitrogen adsorption) were performed, followed by an analysis of 30 carbonation/calcination cycles in a fixed-bed reactor. The mixed metal oxide (CaO−MgO) in the fresh calcined dolomite transformed into separate crystals of CaO and MgO in the cycled sorbent and resulted in a relative decrease in the cyclic CO 2 capture capacity. Favorable structures (decreased crystallinity, increased porosity, and surface area) were generated by water hydration treatment, which was expected to enhance the recyclability, as suggested by some authors. However, this sorbent produced separate Mg and Ca as the major components, leading to a decrease in the CO 2 capture compared to fresh calcined dolomite. Complete segregation between Ca and Mg was observed upon precipitation treatment, which gave rise to the lowest cyclic CO 2 uptake. This segregation was eliminated by the final ball-milling treatment, thereby regaining the original reactivity. These results demonstrate the dominant role of the mixing of Ca and Mg on the cyclic CO 2 capture capacity of dolomite-based sorbents.

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