CO2 capture using mesoporous alumina prepared by a sol-gel process

Mesoporous alumina (MA) having high surface area (812 m2/g) and large pore volume (0.83 cm3/g) with a narrow pore size distribution was prepared by a simple sol-gel process. The as-prepared MA was characterized by XRD, N2 adsorption-desorption isotherms, and transmission electron microscopy (TEM). The CO2 adsorption performance of MA was tested under both low (<1 bar) pressure using a static volumetric system and high pressure (<30 bar) conditions using a gravimetric system. MA demonstrated a CO2 capture capacity of ca. 52 mg/gadsorbent at 1 bar, a value higher than that of a commercial alumina or 3-aminopropyltrimethoxysilane-grafted MCM-41. High pressure (0-30 bar) CO2 adsorption increased in a sequence of commercial alumina < SBA-15 < zeolite 13X < MA. Static adsorption and breakthrough experiments showed that MA offers high separation efficiency for CO2 against N2. CO2 desorption at different temperatures was evaluated in order to identify regeneration conditions of MA after CO2 adsorption. PEI (polyethylenimine)-impregnated MA was also prepared and tested as a CO2 sorbent. The hybrid sorbent material achieved higher CO2 capture capacity (120 mg/gsorbent) than MA alone, with a level comparable to the sorption capacities of PEI functionalized mesoporous silica materials reported to date. Both as-prepared and PEI-impregnated MA exhibited stable adsorption-desorption behaviour during 5 consecutive test cycles.