Sorption of CO2 on NaBr co-doped Li4SiO4 ceramics: Structural and kinetic analysis

Abstract

Structurally modified and improved NaBr co-doped Li4SiO4 ceramics were developed for CO2 absorption in low-CO2-concentration atmospheres. Pure and NaCldoped Li4SiO4 ceramics were also prepared for comparison. The samples were analyzed by X-ray diffraction, Scanning Electron Microscopy, N2 adsorption, X-ray photoelectron spectroscopy, differential scanning calorimetry, and thermogravimetric analyses (dynamic and isothermal). The sorption kinetics were obtained using a double exponential model. The results showed that both Na and Br can be introduced into the Li4SiO4 structure and doped on Li and oxygen sites, respectively. The doped sample presented a Li2O-enriched surface, guaranteeing abundant Li-O sites and our significantly different from previous anionic (CO3, F and Cl) doping of Li4SiO4, Br doping also generated macroporous features with small particle size. These favorable characteristics promoted the surface chemisorption kinetics. Moreover, DSC analysis confirmed the formation of the molten phases during CO2 absorption, which helps improve the lithium diffusion kinetics. Here, 0.1 mol NaBr doping was used to reach a maximum absorption capacity (>30.0 wt.%) in 15 vol.% CO2, suggesting that NaBrdoped Li4SiO4 ceramics have great potential for CO2 capture at high temperature.

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

“…668 Fe-doping of the same material saw little microstructural change as seen by SEM but improved CO 2 absorption that was attributed to the formation of oxygen vacancies due to the substitution of Fe for Cu. 669 Na and Br codoping of Li 4 SiO 4 670 saw improved properties similarly because of the presence of molten species during carbonation, but the effect of Br substitution on O sites also led to phase separation and subsequently a Li 2 O enriched surface, further improving the rate of carbonation. A strategy of promoting Li 4 SiO 4 with NdNO 3 improved the resulting sorbent's performance through the formation of an inert Nd 2 O 3 network to avert sintering at high temperatures.…”

High Temperature CO2 Capture Performance and Kinetic Analysis of Novel Potassium Stannate

“…The very low activation enthalpy for the surface chemisorption indicates that this was not dependent on temperature at this range of temperatures. When compared with other sorbents such as Li4SiO4 [37], the activation enthalpy (∆H ++ ) values of the bulk chemisorption process were greatly reduced, although the temperatures used in that work were lower than in this work. Instead, under similar conditions, the diffusion enthalpy resulted lower in a previous work where Li4SiO4 was also used, indicating larger diffusion resistance by potassium stannate [38].…”

Molten shell-activated, high-performance, un-doped Li4SiO4 for high-temperature CO2 capture at low CO2 concentrations

“…2, the ∆H ++ values for the surface sorption process obtained were 18.7 kJ/mol for MC-0.6. This value is remarkably smaller than the case of other pure Li4SiO4 sorbents using different preparation methods [44,45], implying that surface sorption for MC-0.6 is less reliant on temperature. While for the bulk diffusion period, the ∆H ++ of MC-0.6 was 54.0 kJ/mol, which is smaller than the case of other pure Li4SiO4 sorbents as previously reported [44,45].…”

“…This value is remarkably smaller than the case of other pure Li4SiO4 sorbents using different preparation methods [44,45], implying that surface sorption for MC-0.6 is less reliant on temperature. While for the bulk diffusion period, the ∆H ++ of MC-0.6 was 54.0 kJ/mol, which is smaller than the case of other pure Li4SiO4 sorbents as previously reported [44,45]. Apparently, MC-0.6 has lower activation enthalpies for both the surface-sorption and diffusion processes, mainly attributed by its large specific surface area and small particle/crystal size, which will be confirmed by the following characterization results.…”