Among solid sorbents, the PEI-based materials have attracted much attention and considered as one of promising sorbents for CO2 capture from various gas streams including flue gas and air. However, the amine efficiency of the PEI sorbents reported is still low. When PEI is loaded by impregnation method, its thermal stability is another concern. Recently, we found that using aminopropyltriethoxylsilane (APTES) as a silica surface modification agent can not only improve the CO2 sorption capacity, but also its amine efficiency and thermal stability. In this work, we have examined other modification agents including ethanol, propanol, butanol, propylene oxide, cyclohexene oxide, tetraethyl orthosilicate (TEOS), polyethylene glycol (PEG), epoxybutane, epoxydodcane, in comparison to APTES. Compared to parent fumed silica support, adding the modification agents with hydroxyl groups can promote the CO2 capacity of supported 30wt% PEI sorbent (the capacity of which is 86 mg-CO2/g-s), about 10-38% higher. The improvement follows the order APTES &gt; PEG ~ Epoxydodecane &gt; cyclohexene oxide &gt; others. The PEG-modified sorbents exhibit slightly better regenerability in CO2 adsorption-desorption cycles. Furthermore, we also found that the sorbents prepared by co-impregnation method shows a lightly higher capacity than those prepared by sequential impregnation method. In term of thermal stability, they are similar, all better than the sorbent without modification. In short, support modification with cheap agents could be a promising and cost-effective method to promote the PEI-based sorbents for CO2 capture at low temperatures.

CO2 capture over supported polyethylenimine sorbent: Effect of support modification agent and preparation method

ACS Fall 2021

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