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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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in Wiley Online Library (wileyonlinelibrary.com).Sorption-enhanced glycerol reforming, an integrated process involving glycerol catalytic steam reforming and in situ CO 2 removal, offers a promising alternative for single-stage hydrogen production with high purity, reducing the abundant glycerol by-product streams. This work investigates this process in a fixed-bed reactor, via a two-scale, nonisothermal, unsteady-state model, highlighting the effect of key operating parameters on the process performance. CO 2 adsorption kinetics was investigated experimentally and described by a mathematical reaction-rate model. The integrated process presents an opportunity to improve the economics of green hydrogen production via an enhanced thermal efficiency process, the exothermic CO 2 adsorption providing the heat to endothermic steam glycerol reforming, while reducing the capital cost by removing the processing steps required for subsequently CO 2 separation. The operational time of producing high-purity hydrogen can be enhanced by increasing the adsorbent/catalyst volume ratio, by adding steam to the reaction system and by increasing the inlet reactor temperature.

This work investigates the acidification of a natural limestone source using citric acid in order to produce porous calcium oxide (CaO) CO 2 sorbent, with good stability in high-temperature operation. The CO 2 sorption behavior of the proposed material was studied in several adsorption−regeneration cycles under different adsorption conditions (600, 650, and 700 °C), indicating the superior thermal stability and CO 2 adsorption capacity of the proposed material compared to untreated limestone. Acidification of natural limestone results in the production of a calcium citrate component, which easily decomposes to high-purity fibrous CaO upon calcination at 850 °C. A novel technique based on a controlled atmosphere during the calcination step (two-step treatment) was developed to improve the activity of the CaO sorbent produced from the acidified precursor. A remarkable improvement in the adsorption activity was found for samples prepared using two-step calcination (initially treated in argon, followed by calcination in air) compared to those produced by one-step calcination. The in situ carbon formed during the primary calcination in an argon atmosphere was found to control thermal sintering and promote the dispersion of large agglomerates during burning off in the secondary calcination step under an air atmosphere. The influence of the primary calcination temperature was studied in detail for the acidified sorbents prepared by either one-or two-step calcination.