Enhancement Mechanism of the CO2 Adsorption–Desorption Efficiency of Silica-Supported Tetraethylenepentamine by Chemical Modification of Amino Groups

Tetraethylenepentamine (TEPA) and its derivatives were used to functionalize mesocellular silica foam (MSU-F) supports by wet impregnation for utilization as solid sorbents for CO 2 capture. TEPA derivatives were synthesized by introducing various substituents into the amino groups of TEPA. The CO 2 adsorption and desorption properties of the solid sorbents were evaluated to assess the effects of substituent introduction. TEPA derivatives with bulky alkyl groups such as 3-pentyl (Pe) substituents drastically enhanced the adsorption and regeneration performance of the solid sorbents, while the introduction of hydroxyalkyl substituents had a negative effect on the CO 2 adsorption capacity. The mechanisms governing these effects are discussed in terms of CO 2 affinity and diffusivity, depending on the introduced functionality. For a simulant flue gas of 14% CO 2, 5% O 2, 4% H 2 O, and balance N 2 at 40 °C, MSU-F-supported Pe-TEPA showed a working capacity higher than 4 mmol CO 2 /g by inert-gas sweeping regeneration at 60 °C with excellent cyclic stability. The results demonstrate that the regeneration performance is greatly improved by chemical modification of the amino functional groups of amine-impregnated solid sorbents. This approach is promising for developing low-energy and low-temperature CO 2 capture technologies.