Abstract

A composite sorbent was synthesized by impregnating cylindrical granules of mesoporous γ-Al₂O₃ with an aqueous solution of K₂CO₃. Three fractions of the composite with the characteristic grain size of 1-2 mm, 3-4 mm and 4-6 mm were tested for direct carbon dioxide capture from ambient air in a continuousflow system. It was shown that dynamic CO₂ absorption capacity of the composite sorbent increases significantly with decrease of the characteristic grain size, which indicates that the process is limited by mass transfer. The effect of temperature on thermal regeneration of the composite was also investigated. The change of regeneration temperature from 250 to 300°C enhanced CO₂ absorption capacity for all the fractions studied. XRD in situ study showed that the reason of this enhancement is thermal decomposition of potassium dawsonite KAlCO₃(OH)₂ formed during synthesis of the composite material. The composite sorbent demonstrated a good stability of its CO₂ absorption characteristics, therefore it should be considered as a promising material for direct carbon dioxide capture from air.

Keywords: Carbon dioxide, potassium carbonate, alumina, composite material, absorption, regeneration, air, grain size effect