Mid-temperature CO 2 Adsorption over Different Alkaline Sorbents Dispersed over Mesoporous Al 2 O 3 .

CO 2 adsorbents comprising various alkaline sorption active phases supported on mesoporous Al 2 O 3 were prepared. The materials were tested regarding their CO 2 adsorption behavior in the mid-temperature range, i.e., around 300 °C, as well as characterized via XRD, N 2 physisorption, CO 2 -TPD and TEM. It was found that the Na 2 O sorption active phase supported on Al 2 O 3 (originated following NaNO 3 impregnation) led to the highest CO 2 adsorption capacity due to the presence of CO 2 -philic interfacial Al-O - -Na + sites, and the optimum active phase load was shown to be 12 wt % (0.22 Na/Al molar ratio). Additional adsorbents were prepared by dispersing Na 2 O over different metal oxide supports (ZrO 2 , TiO 2 , CeO 2 and SiO 2 ), showing an inferior performance than that of Na 2 O/Al 2 O 3 . The kinetics and thermodynamics of CO 2 adsorption were also investigated at various temperatures, showing that CO 2 adsorption over the best-performing Na 2 O/Al 2 O 3 material is exothermic and follows the Avrami model, while tests under varying CO 2 partial pressures revealed that the Langmuir isotherm best fits the adsorption data. Lastly, Na 2 O/Al 2 O 3 was tested under multiple CO 2 adsorption-desorption cycles at 300 and 500 °C, respectively. The material was found to maintain its CO 2 adsorption capacity with no detrimental effects on its nanostructure, porosity and surface basic sites, thereby rendering it suitable as a reversible CO 2 chemisorbent or as a support for the preparation of dual-function materials.