High temperature CO2 sorption over modified hydrotalcites

- A K impregnated, Ga substituted microwave aged hydrotalcite was prepared.
- An astonishing CO2 sorption capacity of 2.09 mol/kg was achieved at 573 K.
- Two different kinetic contributions were identified during CO2 uptakes.

Hydrotalcite-like materials were prepared by the co-precipitation method, characterized by PXRD, FTIR, physical adsorption of N2 at 77 K and SEM/EDS, and after calcination they were tested for CO2 sorption at 573 K under dry conditions. The simultaneous effect of aluminum partial substitution with gallium, microwave aging of the precipitated gel and modification with potassium on their sorption capacity was assessed. Sorption isotherms were well described by the Freundlich model for all samples. A remarkable sorption capacity of 2.09 mol/kg at 3.10 bar was obtained for the Ga-containing sample, aged under microwave irradiation and impregnated with 20 wt% of potassium. The sorption kinetics was analyzed from uptake measurements and two distinct contributions (related to fast and slow uptakes), which are considered by the proposed model, were observed. Despite the slower sorption kinetics on the potassium-modified samples, they showed sorption capacities considerably higher than those reported in the literature for commercial hydrotalcites under similar conditions, even for prolonged exposition to CO2.

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