Mid-temperature CO Adsorption over Different Alkaline Sorbents Dispersed over Mesoporous AlO.

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