Development of carbon-based "molecular basket" sorbent for CO ₂ capture

The objective of the present study is to develop a new type of "molecular basket" sorbent (MBS) by using inexpensive and commercially available carbon materials instead of mesoporous silica molecular sieves as supports for CO ₂ capture from flue gas. Several commercial carbon materials, including activated carbons and carbon blacks, with different pore sizes and pore volumes have been used to prepare the carbon-based MBS (CB-MBS) by loading the CO ₂-philic polyethylenimine (PEI) on them. The CO ₂ sorption performance of the prepared CB-MBS was evaluated by using a thermogravimetric analyzer and a fixed-bed flow sorption system. Effects of the pore properties of the carbon supports, PEI loading amount, sorption temperature, and moisture on the sorption capacity were examined. A sorption capacity of 135 mg-CO ₂/g-sorb was obtained by loading 50 wt % PEI on a carbon black, which is almost the same as that of PEI(50)/SBA-15 prepared by loading 50 wt % PEI on SBA-15. The higher CO ₂ sorption capacity of 154 mg-CO ₂/g-sorb was achieved when increasing the PEI loading on the carbon black to 65 wt %. Characterization of the porous structure of the carbon materials indicates that the high sorption capacity of the carbon-black- supported PEI sorbents can be ascribed to their high pore volume and large pore size. It was further found that the volume-based capacity of PEI(50)/C4 was even higher than that of PEI(50)/SBA-15 by 57% due to the higher packing density (0.35 g/mL) of the former than that (0.22 g/mL) of the latter. Because of its high CO ₂ sorption performance and low preparation cost, the carbon-based MBS could be a promising sorbent for cost-efficient CO ₂ capture from flue gas.