In this work, we conducted a study on temperature-programmed desorption (TPD) of CO 2 over molecular basket sorbent (MBS) consisting of polyethylenimine (PEI) immobilized in mesoporous silica SBA-15. A series of MBS sorbents with different PEI loadings in SBA-15 have been studied for CO 2-TPD to gain an insight into the fundamental characteristics of CO 2 sorption/desorption mechanism. Effects of sorption temperature, sorption time, and PEI molecular weight on the CO 2 sorption capacity and desorption behavior of 50 wt% PEI/SBA-15 sorbent were also examined. The results show that two PEI layers, i.e., the exposed PEI layer and the inner bulky PEI layer may exist in PEI/SBA-15 sorbents, and their proportions vary with PEI loading and sorption temperature. Consequently, a two-layer model for CO 2 sorption over PEI/SBA-15 sorbent is proposed, which rationalizes the sorption results with consideration of CO 2 sorption kinetics and thermodynamics. It was also found that CO 2 sorption capacity decreases with increasing PEI molecular weight, which may be mainly attributed to the decrease of primary amine content and the increase of tertiary amine content as well as increased interactions between polymeric chains in the PEI molecules.
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