Cyclic CO2 absorption/desorption property of Li3NaSiO4 under the partial pressure of CO2 for practical applications

The temperature for realizing the cyclic CO2 absorption/desorption property of Li3NaSiO4 by repetition of switching a CO2/N2 gas mixture and N2 with a partial pressure of CO2, P(CO2), of 0.1 bar was optimized using the pseudo van't Hoff plot of LiNaCO3 + Li2SiO3 ↔ Li3NaSiO4 + CO2 prepared by thermogravimetry at various P(CO2) values.

A new method for the preparation of high-purity CO2-absorbing Li3NaSiO4 powder using lithium silicate and sodium carbonate

The starting materials and temperature for the preparation of Li₃NaSiO₄ powder, which has attracted attention as a CO₂ absorbent, were optimized in this study. Mixtures of Li₂CO₃, Na₂CO₃, and SiO₂ as well as Li₄SiO₄, Li₂SiO₃, and Na₂CO₃ were subjected to thermogravimetry-differential thermal analysis (TG-DTA) to elucidate their reaction mechanisms. The phase, morphology, specific surface area, and CO₂ absorption characteristics of the powder specimens that were obtained by heating the two mixtures were examined by X-ray diffraction (XRD), secondary electron microscopy (SEM), N₂ adsorption isotherm and isothermal TG-DTA. Melted LiNaCO₃ was generated via the heat treatment of the Li₂CO₃, Na₂CO₃, and SiO₂ powder mixture, yielding a low-purity bulk specimen with inhomogeneous particle size. However, the use of the Li₄SiO₄, Li₂SiO₃, and Na₂CO₃ mixture as a starting material ensured that no liquid phase was generated during heat treatment and successfully yielded Li₃NaSiO₄ powder which was purer than the product derived from the Li₂CO₃/Na₂CO₃/SiO₂ mixture, presumably because of the lower volatility of Li and Na in the solid phase than that in the liquid phase of LiNaCO₃. The Li₃NaSiO₄ powder derived from Li₄SiO₄, Li₂SiO₃, and Na₂CO₃ showed a slightly larger surface area with homogeneous particle size and almost identical CO₂ absorption kinetics compared to those of the product obtained from Li₂CO₃, Na₂CO₃, and SiO₂, in addition to absorbing a higher amount of CO₂ owing to its higher purity.

CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances

Carbon dioxide capture and mitigation form a key part of the technological response to combat climate change and reduce CO₂ emissions. Solid materials capable of reversibly absorbing CO₂ have been the focus of intense research for the past two decades, with promising stability and low energy costs to implement and operate compared to the more widely used liquid amines. In this review, we explore the fundamental aspects underpinning solid CO₂ sorbents based on alkali and alkaline earth metal oxides operating at medium to high temperature: how their structure, chemical composition, and morphology impact their performance and long-term use. Various optimization strategies are outlined to improve upon the most promising materials, and we combine recent advances across disparate scientific disciplines, including materials discovery, synthesis, and in situ characterization, to present a coherent understanding of the mechanisms of CO₂ absorption both at surfaces and within solid materials.