Utilization of mesoporous alumina-based supports synthesized by a surfactant-assisted technique for post-combustion CO2 capture

This research investigates the effect of textural properties, including surface area, pore size, and pore volume, on the capturing performance of mesoporous alumina supported K2CO3. The supports were synthesized using a surfactant-assisted technique with two types of non-ionic amphiphilic triblock copolymers, PEG-PPG-PEG Pluronic (R) P-123 and Pluronic P31R1, and the cationic surfactant of cetyltrimethylammonium bromide (C-TAB). In the synthesis of the supports, various surfactant-to-Al molar ratios were used to obtain different textural properties. Then, as-synthesized supports were employed to prepare K2CO3-based sorbents using a dry impregnation method. Sorbents prepared by the supports containing higher surfactant-to-Al ratios showed improved capturing performance due to an enhancement in the pore size and pore volume. Larger pore size and pore volume facilitate K2CO3 penetration into the supports' pores during the impregnation process and lead to the proper coating of K2CO3 on the surface. Among the synthesized supports, the one prepared by C-TAB with a surfactant-to-Al ratio of 0.5 represented the highest CO2 uptake (5.7 mmol CO2/g K2CO3) and remained stable over fifteen carbonation/regeneration cycles. In general, sorbents prepared by C-TAB represented a higher average surface area than the other sorbents. Hence, they provided more active sites for the carbonation reactions, resulted in improved capturing performance. The effect of K2CO3 loading was investigated on the CO2 capture capacity of the sorbents, and the optimum loading was found to be 40-50 wt%. At higher loadings, the pore volume and surface area decreased significantly due to pore blockage; thus, a significant decline in the CO2 uptake occurred.