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A high-temperature regenerable CO2 absorbent, Zr-stabilized CaO, was prepared using the surfactant template-ultrasound synthesis method in this work. During 15 absorption/desorption cycles, it was found that Zr-stabilized CaO with a Zr/Ca molar ratio of 0.303 kept the most favorable stability and CO2 uptake capacity among the proposed Zr-stabilized samples. During multiple carbonation/decarbonation cycles, the incorporation of zirconium inhibited the agglomeration and sintering of CaO particles, thereby improving the absorbent durability. The effects of carbonation temperature (600–700 °C) and surfactant amount used in the preparation method on the performance of the proposed absorbent were investigated. The results showed that an excess of surfactant negatively affects the absorbent structural stability. Multicycle CO2 capture tests carried out between 600 and 700 °C showed that an increase in carbonation temperature improved the absorption capacity and durability of the proposed Zr-stabilized CaO absorbent. In summary, the results showed a superior prolonged stability of Zr-stabilized CaO as compared to pure CaO under severe operating conditions.

Porous nanoparticle lithium zirconate (Li 2 ZrO 3 ) was prepared using an ultrasound-assisted surfactant-template method in the liquid-state reaction. The CO 2 adsorption performance of the prepared materials was tested under various conditions and compared with that of Li 2 ZrO 3 prepared by the simple surfactant-template method (porous, without sonication) and the conventional soft-chemistry route. The results indicated a better adsorption rate and capacity of porous nanopowders, whether assisted with ultrasound or not, in comparison with the traditional sample. This behavior is mainly due to a less aggregated powder structure and porous framework, facilitating gas and ion diffusion to and from the particle layers. However, the porous adsorbent prepared without sonication exhibited instability during cyclic operation, limiting its application for long-time use. Sonication time and surfactant concentration were found to be key parameters for controlling the crystallite size and the BET surface area. The porous Li 2 ZrO 3 sample prepared with less surfactant and a shorter irradiation time (sample A) had the most favorable sorption kinetics and capacity among all studied samples. The maximum uptake capacity of 22 wt % for sample A compared to 15.2 wt % for the conventional sample (sample J, fabricated by the soft-chemistry method), obtained under a 100% CO 2 stream, suggested a noticeable improvement in sorption behavior of the proposed adsorbents compared with traditional Li 2 ZrO 3 . Moreover, the adequate cyclic stability of porous powders prepared by sonication identify these materials as promising CO 2 acceptors, particularly for integrated sorbent/catalyst systems such as that used for sorption-enhanced steam methane reforming (SESMR). CO 2 adsorption experimental data for sample A were successfully modeled at various CO 2 partial pressures using a double-exponential equation.

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