A virgin activated carbon, denoted as AR, was successfully modified through Polyethylenimine (PEI) impregnation. Virgin and PEI-impregnated samples were tested for CO2 capture under post-combustion conditions (53 °C, 15 % CO2/85 % N2) by using a thermogravimetric analyser (TGA). The influence of the PEI/AR ratio, the stirring time of the mixture PEI/solvent/AR and the solvent type on the CO2 sorption capacity of the modified carbons was also assessed. Maximum uptakes were given by the following conditions: PEI addition up to 80 % of initial weight, stirring time of 8 h and methanol as solvent. In particular, longer agitation (which was never studied before according to the author’s knowledge) facilitated higher uptakes. This was likely due to a better dispersion of the polymer onto the support’s pores. N2 adsorption measurements revealed a reduction of surface areas and pore volumes due to the presence of the polymer inside the carbon’s pores. Nevertheless, all the modified samples exhibited larger uptakes than that of the virgin carbon, whose CO2 capacity was increased by up to four times. This outstanding enhancement was attributed to the N-based functionalities incorporated onto the pristine carbon’s surface after the PEI impregnation. These were detected by appropriate techniques, confirming the effectiveness of the surface modification. This result is corroborated by the increased N content measured for PEI-modified samples by elemental analysis (CHNS). The presence of N-containing groups ensured a higher selectivity of the sorbents toward carbon dioxide. Furthermore, the optimally PEI-impregnated carbon showed larger uptakes and faster kinetics than those attained by Zeolite-13X, included for comparison purposes. In addition to this, its CO2 sorption capacity under post-combustion conditions remained nearly unaltered over 10 Temperature Swing Adsorption (TSA) cycles. The durability shown by the optimally modified carbon was likely due to the thermal stability of the polymer. The cyclic test also showed that the sorbent was easily regenerated at 120 °C, thus potentially implying a low energy penalty for a fossil-fueled power plant. These findings indicate that optimised PEI impregnation is an effective route to enhance the post-combustion CO2 capture performance of activated carbon. Moreover, PEI impregnated carbon could represent a competitive alternative to the use of liquid amines in the conventional absorption process.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)