Surfactant-Mediated Lithium Orthosilicate Composite Enables Rapid High-Temperature Co2 Absorption

A novel surfactant-assisted approach to preparing a nanostructured lithium orthosilicate (LOS) has been developed by adding a polyether amine surfactant to aqueous citrate sol-gel. The ratio of surfactant to SiO2 was critical to producing an LOS that is stable to carbonation/decarbonation cycles. Preferred LOS compositions sorb 26 wt % CO2 within 1 min from a 50 vol % CO2/N-2 stream and show no observed loss in a 33 wt % working capacity in 1 h isothermal steam cycles. The novel synthetic approach generates a product-like precursor phase with nanoscale domains of lithium metasilicate and lithium carbonate stabilized by a carbonaceous component that originates from the degradation of citrate and surfactant species. This composition is required to achieve an LOS with properties enabling sorption-enhanced catalysis. Physically meaningful rate constants and diffusivities are provided by a piecewise adaptation of the Ishida and Wen core-shell model, confirming faster reaction and diffusion kinetics for these high-performing LOS. An overall working hypothesis of key results helps to explain robustness in sorption cycling and suggests the advantages of a product-focused sorbent design.