Impregnation Precipitation Preparation and Kinetic Analysis of Li4SiO4-Based Sorbents with Fast CO2 Adsorption Rate

High-temperature CO2 sorption over Li4SiO4 synthesized from diatomite: study of sorption heat and isotherm modeling

The Li4SiO4 seems to be an excellent sorbent for CO2 capture at post-combustion. Our work contributes to understanding the effect of the natural Algerian diatomite as a source of SiO2 in the synthesis of Li4SiO4 for CO2 capture at high temperature. For this purpose, we use various molar % (stoichiometric and excess) of calcined natural diatomite and pure SiO2. To select the best composition, CO2 sorption isotherms at 500 °C on the prepared Li4SiO4 are obtained using TGA measurements under various flows of CO2 in N2. The sorbent having 10% molar SiO2 in diatomite (10%ND-LS) exhibits the best CO2 uptake, probably due to various factors such as the content of the different secondary phases. A comparative study was performed at 400 to 500 °C on this selected 10%ND-LS and those with stoichiometric composition obtained with diatomite and pure SiO2. The obtained isotherms show the endothermic character of CO2 sorption. In addition, the evolution of isosteric heat highlights the nature of the involved CO2/Li4SiO4 interactions, by considering the double-shell mechanism. Finally, the experimental sorption isotherms are confronted with some well-known adsorption models to explain the phenomenon occurring over our prepared sorbents. Freundlich and Jensen-Seaton models present a better correlation with the experimental results.

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.

Lithium silicate nanosheets with excellent capture capacity and kinetics with unprecedented stability for high-temperature CO2 capture

An excessive amount of CO₂ is the leading cause of climate change, and hence, its reduction in the Earth's atmosphere is critical to stop further degradation of the environment. Although a large body of work has been carried out for post-combustion low-temperature CO₂ capture, there are very few high temperature pre-combustion CO₂ capture processes. Lithium silicate (Li₄SiO₄), one of the best known high-temperature CO₂ capture sorbents, has two main challenges, moderate capture kinetics and poor sorbent stability. In this work, we have designed and synthesized lithium silicate nanosheets (LSNs), which showed high CO₂ capture capacity (35.3 wt% CO₂ capture using 60% CO₂ feed gas, close to the theoretical value) with ultra-fast kinetics and enhanced stability at 650 °C. Due to the nanosheet morphology of the LSNs, they provided a good external surface for CO₂ adsorption at every Li-site, yielding excellent CO₂ capture capacity. The nanosheet morphology of the LSNs allowed efficient CO₂ diffusion to ensure reaction with the entire sheet as well as providing extremely fast CO₂ capture kinetics (0.22 g g⁻¹ min⁻¹). Conventional lithium silicates are known to rapidly lose their capture capacity and kinetics within the first few cycles due to thick carbonate shell formation and also due to the sintering of sorbent particles; however, the LSNs were stable for at least 200 cycles without any loss in their capture capacity or kinetics. The LSNs neither formed a carbonate shell nor underwent sintering, allowing efficient adsorption–desorption cycling. We also proposed a new mechanism, a mixed-phase model, to explain the unique CO₂ capture behavior of the LSNs, using detailed (i) kinetics experiments for both adsorption and desorption steps, (ii) in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy measurements, (iii) depth-profiling X-ray photoelectron spectroscopy (XPS) of the sorbent after CO₂ capture and (iv) theoretical investigation through systematic electronic structure calculations within the framework of density functional theory (DFT) formalism.

Capturing CO₂ before its release. Lithium silicate nanosheets showed high CO₂ capture capacity (35.3 wt%) with ultra-fast kinetics (0.22 g g⁻¹ min⁻¹) and enhanced stability at 650 °C for at least 200 cycles, due to mixed-phase-model of CO₂ capture.

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.

Solid-Waste-Derived Carbon Dioxide-Capturing Materials

Solid sorbents are considered to be promising materials for carbon dioxide capture. In recent years, many studies have focused on the use of solid waste as carbon dioxide sorbents. The use of waste resources as carbon dioxide sorbents not only leads to the development of relatively low-cost materials, but also eliminates waste simultaneously. Different types of waste materials from biomass, industrial waste, household waste, and so forth were used as carbon dioxide sorbents with sufficient carbon dioxide capture capacities. Herein, progress on the development of carbon dioxide sorbents produced from waste materials is reviewed and covers key factors, such as the type of waste, preparation method, further modification method, carbon dioxide sorption performance, and kinetics studies. In addition, a new research direction for further study is proposed. It is hoped that this critical review will not merely sum up the major research directions in this field, but also provide significant suggestions for future work.

Performance of Li₄SiO₄ Material for CO₂ Capture: A Review

Lithium silicate (Li₄SiO₄) material can be applied for CO₂ capture in energy production processes, such as hydrogen plants, based on sorption-enhanced reforming and fossil fuel-fired power plants, which has attracted research interests of many researchers. However, CO₂ absorption performance of Li₄SiO₄ material prepared by the traditional solid-state reaction method is unsatisfactory during the absorption/regeneration cycles. Improving CO₂ absorption capacity and cyclic stability of Li₄SiO₄ material is a research highlight during the energy production processes. The state-of-the-art kinetic and quantum mechanical studies on the preparation and CO₂ absorption process of Li₄SiO₄ material are summarized, and the recent studies on the effects of preparation methods, dopants, and operating conditions on CO₂ absorption performance of Li₄SiO₄ material are reviewed. Additionally, potential research thoughts and trends are also suggested.

Low-Temperature and Fast Kinetics for CO2 Sorption Using Li6WO6 Nanowires

In this paper, lithium hexaoxotungstate (Li₆WO₆) nanowires were synthesized via facile solid-state reaction and were tested for CO₂ capture applications at both low (<100 °C) and high temperatures (>700 °C). Under dry conditions, the nanowire materials were able to capture CO₂ with a weight increment of 12% in only 60 s at an operating temperature of 710 °C. By contrast, under humidified ambience, Li₆WO₆ nanowires capture CO₂ with weight increment of 7.6% at temperatures as low as 30-40 °C within a time-scale of 1 min. It was observed that the CO₂ chemisorption in Li₆WO₆ is favored in the oxygen ambience at higher temperatures and in the presence of water vapor at lower temperatures. Nanowire morphology favors the swift lithium supply to the surface of lithium-rich Li₆WO₆, thereby enhancing the reaction kinetics and lowering time scales for high capacity adsorption. Overall, high chemisorption capacities, superfast reaction kinetics, wide range of operating temperatures, and reasonably good recyclability make 1-D Li₆WO₆ materials highly suitable for various CO₂ capture applications.

Lithium orthosilicate with halloysite as silicon source for high temperature CO2 capture

Lithium orthosilicate (Li₄SiO₄)-based sorbents were synthesized using a low cost and naturally available mineral resource (halloysite) as silicon source for high temperature CO₂ capture.

Thermal conversion of a tailored metal–organic framework into lithium silicate with an unusual morphology for efficient CO2 capture

Thermal conversion of a Li- and Si-containing MOF produces ceramic Li₄SiO₄ with a coral-like morphology, which is an advanced CO₂ absorbent with high uptake and fast absorption.

Triethylenetetramine-Modified P123-Occluded Zr-SBA-15 Molecular Sieve for CO2 Adsorption

A pluronic 123 (P123)-occluded mesoporous molecular sieve Zr-SBA-15, Zr-SBA(P) was modified with triethylenetetramine (TETA) and tested for CO2 adsorption. The synthesized materials were characterized by powder X-ray diffraction, N2 adsorption–desorption, dispersive spectroscopy, thermogravimetric analysis, temperature-programmer desorption of CO2, and Fourier transform infrared spectroscopy. The results of CO2 adsorption show that the TETA and P123 species have positive effects on the CO2 adsorption capacity of the adsorbent, and the performance of the as-prepared adsorbent in a stream of low CO2 concentration is excellent. At 50 wt-% TETA loading, Zr-SBA(P) has a maximum capacity of 4.27 mmol g–1 in a stream of 5 % CO2 at 50°C, ~33.5 % higher than the adsorbent prepared in the absence of P123. In addition, the adsorbent is superior in reusability. It is envisaged that the adsorbent will find wide application in CO2 capture.