Self-Activation Mechanism Investigations on Large K2CO3-Doped Li4SiO4 Sorbent Particles

Elucidating the promotion of Na2CO3 in CO2 capture by Li4SiO4

Although Li₄SiO₄-based sorbents are candidates for CO₂ capture at high temperatures, it is still necessary to improve their kinetic activation for adsorption and desorption. Carbonate doping to Li₄SiO₄ is considered as one of the effective means to improve CO₂ capture by Li₄SiO₄. In this study, Li₄SiO₄ was synthesized using Li₂CO₃ and SiO₂ at 900 °C, and mixed with different amounts of Na₂CO₃ as CO₂ sorbents. The effects of Na₂CO₃ on the absorption and desorption were characterized using thermal analyses in an atmosphere of 80 vol% CO₂-20 vol% N₂. In situ Raman and XRD were used for the characterization of the structural transformations and phase evolution during the CO₂ capture. The activation energy of both chemisorption and diffusion in adsorption dropped significantly. The additive Na₂CO₃ can react with CO₂ and produce the pyrocarbonate, which is favorable for CO₂ capture of Li₄SiO₄ and CO₂ diffusion. The doped Na₂CO₃ served two functions: producing the intermediate product and forming the melt with the product Li₂CO₃ to accelerate CO₂ transport. The Na₂CO₃-doped Li₄SiO₄ exhibits stable cyclic durability with conversions of 75% in 20 adsorption-desorption cycles.

Thermodynamics and kinetics analyses of high CO2 absorption properties of Li3NaSiO4 under various CO2 partial pressures

The temperature and P(CO₂) region for the reaction between Li₃NaSiO₄ and CO₂ is similar to that of Li₄SiO₄. However, Li₃NaSiO₄ shows higher CO₂ absorption kinetics.

Hydrothermal synthesis and methylene blue adsorption performance of novel 3D hierarchical Li2Si2O5 hydrate particles

Li₂Si₂O₅ are generally obtained in form of granules with unavoidable impurities including Li₂SiO₃ and SiO₂. Here, we demonstrated a facile hydrothermal route to synthesize novel 3D hierarchical Li₂Si₂O₅ hydrate hollow flower-like microstructures assembled by rod subunits with high purity. The crystal growth was accomplished by complete transformation from poorly crystallized metastable phases formed in the initial stage including Li₂SiO₃, SiO₂ and various Li₂Si₂O₅ hydrate species to Li₂Si₂O₅ hydrate rods. The transformation over many times gave a sustainable high chemical potential to direct the anisotropic growth of Li₂Si₂O₅ hydrate rods with large aspect ratios. Besides, the variation of Li/Si molar ratios confirmed that Li₂Si₂O₅ hydrate rods were obtained only at Li/Si = 1. The perfection and aspect ratio of the rods could be controlled very well by adjusting the hydrothermal temperatures and precursor concentrations. Some new points about obtaining pure phase and anisotropic morphology were discussed, including careful selection of precursors and synthetic method. The obtained novel 3D Li₂Si₂O₅ hydrate structures exhibited a characteristic of mesoporous material and had an excellent adsorption capability of methylene blue with high adsorption amount of 49.42 mg·g⁻¹ and color removal of 98.85%, indicating the potential use in wastewater treatment.

Industrial carbon dioxide capture and utilization: state of the art and future challenges

This review covers the sustainable development of advanced improvements in CO₂ capture and utilization.

Preparation of Novel Li4 SiO4 Sorbents with Superior Performance at Low CO2 Concentration

This work produced Li4 SiO4 sorbents through an impregnated-suspension method to overcome its typical poor performance at low CO2 concentrations. A SiO2 colloidal solution and two different organic lithium precursors were selected. A bulgy surface morphology (and thus, the significantly enlarged reacting surface area) was obtained for Li4 SiO4 , which contributed to the high absorption capacity. As a result, the capacity in cyclic tests at 15 vol % CO2 was approximately 8 times higher than conventional Li4 SiO4 prepared through a solid-state reaction. The phenomenon of a progressively increasing capacity (i.e., sustainable usage) was observed over the 40 cycles investigated, and this increasing trend continued to the last cycle. Correspondingly, over the course of the multicycle absorption/ desorption processes, the sorbents evolve from lacking porosity to having a high number of micron-sized pores.

Operando Raman spectroscopic studies of lithium zirconates during CO2 capture at high temperature

Operando Raman spectroscopy allowed following up the phase evolution for K-doped lithium zirconates during the CO₂ capture process.