Hydrogen production from dry reforming of methane, using CO2 previously chemisorbed in the Li6Zn1-xNixO4 solid solution

Li6ZnO4 was chemically modified by nickel addition, in order to develop different compositions of the solid solution Li6Zn1-xNixO4. These materials were evaluated bifunctionally; analyzing their CO2 capture performances, as well as on their catalytic properties for H2 production via dry reforming of methane (DRM). The crystal structures of Li6Zn1-xNixO4 solid solution samples were determined through X-ray diffraction, which confirmed the integration of nickel ions up to a concentration around 20 mol%, meanwhile beyond this value, a secondary phase was detected. These results were supported by XPS and TEM analyses. Then, dynamic and isothermal thermogravimetric analyses of CO2 capture revealed that Li6Zn1-xNixO4 solid solution samples exhibited good CO2 chemisorption efficiencies, similarly to the pristine Li6ZnO4 chemisorption trends observed. Moreover, a kinetic analysis of CO2 isothermal chemisorptions, using the Avrami-Erofeev model, evidenced an increment of the constant rates as a function of the Ni content. Since Ni2+ ions incorporation did not reduce the CO2 capture efficiency and kinetics, the catalytic properties of these materials were evaluated in the DRM process. Results demonstrated that nickel ions favored hydrogen (H2) production over the pristine Li6ZnO4 phase, despite a second H2 production reaction was determined, methane decomposition. Thereby, Li6Zn1-xNixO4 ceramics can be employed as bifunctional materials.

Visible-light-driven photocatalysis of carbon dioxide and organic pollutants by MFeO2 (M = Li, Na, or K)

In recent years, lithium-containing ceramic materials have attracted considerable research attention as high-temperature adsorbents of carbon dioxide. The recycling of electrode materials from spent lithium-ion batteries for use as photocatalysts in recovering CO₂ and degrading organic pollutants is worthy of exploration. Solid, magnetic ferrite-containing photocatalysts are easily separated from reaction solutions by using magnetic devices. Solid catalysts (e.g., LiFeO₂, LiFe₅O₈, NaFeO₂, and K₂Fe₂O₄) were prepared through the calcination of Fe₂O₃ and M₂CO₃. CO₂ was photoreduced and crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) were photodegraded under visible light irradiation. The optimized K₂Fe₂O₄ photocatalyst increased the rate of photocatalytic conversion from CO₂ to methane at 20.9 µmol g^-1 h^-1. The catalytic efficiency indicated that the optimized reaction rate constants of CV with LiFeO₂, NaFeO₂, and K₂Fe₂O₄ were 2.98 × 10^-1, 5.32 × 10^-1, and 4.36 × 10^-1 h^-1, respectively. The quenching effect achieved through the use of various scavengers and the electron paramagnetic resonance in CV degradation revealed the substantial contribution of the reactive superoxide anion radical O₂^- and the minor roles of h⁺ and the OH radical. Its usefulness in the synthesis of solid-base catalyst MFeO₂ is promising for environmental control and relevant applications, particularly in solar energy manufacturing.

New approach to consecutive CO oxidation and CO2 chemisorption using Li2CuO2 ceramics modified with Na- and K-molten salts

The addition of alkali carbonates to Li₂CuO₂ improved the CO oxidation and the subsequent CO₂ with a high ratio of captured/released CO₂. Materials modified with a single carbonate presented the best enhancement for the removal of both CO_X.

Enhancing CO2 chemisorption on lithium cuprate (Li2CuO2) at moderate temperatures and different pressures by alkaline nitrate addition

Reaction mechanism description of CO₂ capture on alkaline (Li, Na and K) nitrate-containing Li₂CuO₂ at moderate temperatures.

Evaluation of Fe-containing Li2CuO2 on CO2 capture performed at different physicochemical conditions

Li₂CuO₂ and different iron-containing Li₂CuO₂ samples were synthesized by solid state reaction. On iron-containing samples, atomic sites of copper are substituted by iron ions in the lattice (XRD and Rietveld analyses). Iron addition induces copper release from Li₂CuO₂, which produce cationic vacancies and CuO, due to copper (Cu²⁺) and iron (Fe³⁺) valence differences. Two different physicochemical conditions were used for analyzing CO₂ capture on these samples; (i) high temperature and (ii) low temperature in presence of water vapor. At high temperatures, iron addition increased CO₂ chemisorption, due to structural and chemical variations on Li₂CuO₂. Kinetic analysis performed by first order reaction and Eyring models evidenced that iron addition on Li₂CuO₂ induced a faster CO₂ chemisorption but a higher thermal dependence. Conversely, CO₂ chemisorption at low temperature in water vapor presence practically did not vary by iron addition, although hydration and hydroxylation processes were enhanced. Moreover, under these physicochemical conditions the whole sorption process became slower on iron-containing samples, due to metal oxides presence.

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.

Kinetic analysis for cyclic CO2 capture using lithium orthosilicate sorbents derived from different silicon precursors

The illustration of the CO₂ sorption process in Li₄SiO₄.