Parametrical Study on CO₂ Capture from Ambient Air Using Hydrated K₂CO₃ Supported on an Activated Carbon Honeycomb

Potassium carbonate is a highly hygroscopic salt, and this aspect becomes important for CO₂ capture from ambient air. Moreover, CO₂ capture from ambient air requires adsorbents with a very low pressure drop. In the present work an activated carbon honeycomb monolith was coated with K₂CO₃, and it was treated with moist N₂ to hydrate it. Its CO₂ capture capacity was studied as a function of the temperature, the water content of the air, and the air flow rate, following a factorial design of experiments. It was found that the water vapor content in the air had the largest influence on the CO₂ adsorption capacity. Moreover, the deliquescent character of K₂CO₃ led to the formation of an aqueous solution in the pores of the carrier, which regulated the temperature of the CO₂ adsorption. The transition between the anhydrous and the hydrated forms of potassium carbonate was studied by means of FT-IR spectroscopy. It can be concluded that hydrated potassium carbonate is a promising and cheap alternative for CO₂ capture from ambient air for the production of CO₂-enriched air or for the synthesis of solar fuels, such as methanol.