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Abstract
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Highly stabilized mesoporous core–shell-structured CaO-based spheriform CO2 sorbents are fabricated, for the first time, by a novel repeated impregnation coating process combined with the mesoscopic surfactant-templating method. By adopting our established wet-coating strategy along with a sol–gel process, different mesoporous material-shelled sorbents with various shell thicknesses (1–5 ?m) and shell compositions (silica/zirconia or pure zirconia) are synthesized. Cyclic CO2 capture performance is tested in a thermogravimetric analyzer with the core–shell pellet sorbents with a ?1 ?m mesoporous zirconia shell exhibiting an unprecedented CO2 uptake capacity of ?7.2 moles CO2 per kg decarbonated sorbent and the lowest activity loss of only 30.8% after 20 cycles. This is attributed to the unique core–shell coating strategy in which the thermally stable Zr species prevent the aggregation and overgrowth of CaO crystals and sorbent sintering. When comparing the core–shell sorbents with Si-contained mesoporous shells, zirconia shelled ones exhibit significantly more outstanding performance. An attrition study using an air-jet apparatus under the standard test method reveals that the mesoporous zirconia shelled sorbent exhibits enhanced attrition resistance, which is also attributed to the novel core–shell design, offering protection for the reactive core.
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