Experimental and kinetics investigations of low-concentration CO2 adsorption on several amine-functionalized adsorbents

The rapid cleanup of endogenous CO 2 has become a necessity in environmental control and life support systems (ECLSSs), to ensure crew safety and long-term task execution. The extensively used non-regenerable LiOH and soda lime adsorbents, although exhibit high CO 2 storage capacities and fast kinetics, can hardly fulfill the demands of reduced launch weight and storage volume in the space- and load-limited ECLSSs. New CO 2 adsorbents with desirable attributes including high CO 2 uptakes, good selectivity , facile regeneration, fast adsorption and desorption kinetics, and good multicycle stability are urgently needed. We developed amine-functionalized adsorbents by loading tetraethylenepentamine (TEPA) on mesoporous supports of activated carbon (AC), aluminum oxide (AO) and silica gel (SG). The adsorbents were characterized by N 2 adsorption-desorption, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) to study their microstructural properties. CO 2 adsorption capacities and kinetic performance of the adsorbents with different supports and various amine loadings (10–50 wt%) were evaluated in 2%CO 2 at 20 °C. The effects of support and amine loading on the structure-performance relationships of the adsorbents were demonstrated. The TEPA-SG-20 adsorbent (20 wt% TEPA loaded on silica gel support) exhibits the highest CO 2 adsorption capacity of 1.90 mmol CO 2 /g and the maximum amine efficiency of 0.48 mmol CO 2 /mmol N. TEPA-SG-20 also exhibits fast CO 2 adsorption kinetics , and the Avrami fractional order kinetic model provides a satisfactory correlation of the experimental CO 2 uptakes. Furthermore, the TEPA-SG-20 adsorbent can be efficiently regenerated at 110 °C with a great regeneration efficacy of 97%. The desired adsorbent also exhibits good working stability with a low loss-in-capacity of 4.32% in 10 consecutive cycles. The good CO 2 adsorption performance of TEPA-SG-20 is associated with the excellent microstructural properties such as high surface area, great pore volume and uniform dispersion of amine species. Overall, the desired TEPA-SG-20 adsorbent shows promise for low-concentration CO 2 removal in ECLSSs.