Sol-gel Synthesis of MgAl2O4-stabilized CaO for CO2 Capture

Mechanistic Understanding of CaO-Based Sorbents for High-Temperature CO2 Capture: Advanced Characterization and Prospects

Carbon dioxide capture and storage technologies are short to mid-term solutions to reduce anthropogenic CO₂ emissions. CaO-based sorbents have emerged as a viable class of cost-efficient CO₂ sorbents for high temperature applications. Yet, CaO-based sorbents are prone to deactivation over repeated CO₂ capture and regeneration cycles. Various strategies have been proposed to improve their cyclic stability and rate of CO₂ uptake including the addition of promoters and stabilizers (e. g., alkali metal salts and metal oxides), as well as nano-structuring approaches. However, our fundamental understanding of the underlying mechanisms through which promoters or stabilizers affect the performance of the sorbents is limited. With the recent application of advanced characterization techniques, new insight into the structural and morphological changes that occur during CO₂ uptake and regeneration has been obtained. This review summarizes recent advances that have improved our mechanistic understanding of CaO-based CO₂ sorbents with and without the addition of stabilizers and/or promoters, with a specific emphasis on the application of advanced characterization techniques.

A Review on New 3-D Printed Materials' Geometries for Catalysis and Adsorption: Paradigms from Reforming Reactions and CO2 Capture

"Bottom-up" additive manufacturing (AM) is the technology whereby a digitally designed structure is built layer-by-layer, i.e., differently than by traditional manufacturing techniques based on subtractive manufacturing. AM, as exemplified by 3D printing, has gained significant importance for scientists, among others, in the fields of catalysis and separation. Undoubtedly, it constitutes an enabling pathway by which new complex, promising and innovative structures can be built. According to recent studies, 3D printing technologies have been utilized in enhancing the heat, mass transfer, adsorption capacity and surface area in CO2 adsorption and separation applications and catalytic reactions. However, intense work is needed in the field to address further challenges in dealing with the materials and metrological features of the structures involved. Although few studies have been performed, the promise is there for future research to decrease carbon emissions and footprint. This review provides an overview on how AM is linked to the chemistry of catalysis and separation with particular emphasis on reforming reactions and carbon adsorption and how efficient it could be in enhancing their performance.

Reactivity Improvement of Ca-Based CO2 Absorbent Modified with Sodium Humate in Cyclic Calcination/Carbonation

The Ca-based sorbent cyclic calcination/carbonation reaction (CCCR) is a high-efficiency technique for capturing CO₂ from combustion processes. The CO₂ capture ability of CaO modified with sodium humate (HA-Na) (HA-Na/CaO) in long-term calcination/carbonation cycles was investigated. The enhancement mechanism of HA-Na on CCCR was proposed and demonstrated. The effects of carbonation temperature, reaction duration, and the addition amount of HA-Na on the carbonation rate of the CaO adsorbent were also studied. HA-Na/CaO is allowed to react 20 min at the optimum conditions for calcination (920 °C, 100% N₂) and for carbonation (700 °C, 15% CO₂, 85% N₂), respectively. HA-Na plays a key role in the CCCR process, and the carbonation conversion rate is lifted obviously. The maximum conversion rate of HA-Na/CaO is 23% higher than that of CaO in the first cycle. After 20 cycles, the conversion rate of HA-Na/CaO is still 0.28, while that of CaO is only 0.15. The carbonation conversion rate for HA-Na/CaO is improved by 86% compared to CaO. In addition, the characteristics of calcined sorbents are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) methods.

Bi-functional Ru/Ca3Al2O6–CaO catalyst-CO2 sorbent for the production of high purity hydrogen via sorption-enhanced steam methane reforming

Sorption-enhanced steam methane reforming (SE-SMR) combines steam methane reforming and a CO₂ abstraction reaction to yield high purity hydrogen.