Direct Air Capture of CO<sub>2</sub> with Metal Nitrate-Doped, Tetraethylenepentamine-Functionalized SBA-15 Adsorbents
Heng Wang, Zuoyan Yang, Yuqi Zhou, Hongjie Cui, Zhenmin Cheng, Zhiming Zhou
Abstract
Direct air capture (DAC) by solid amine adsorbents is a promising route to mitigate CO 2 emissions from distributed sources and confined spaces. However, a capacity–stability trade-off of supported amine adsorbents often exists for DAC applications. Herein, we report that a KNO 3 -doped, tetraethylenepentamine (TEPA)-functionalized SBA-15 adsorbent (i.e., 50TEPA-4.5K/SBA-15) has a high CO 2 adsorption capacity and good cycling stability for DAC. 50TEPA-4.5K/SBA-15 is synthesized by successive impregnation of KNO 3 (4.5 wt %) and TEPA (50 wt %) onto SBA-15 and evaluated using a fixed-bed adsorber in cyclic operation (adsorption at 30 °C in 440 ppm of CO 2 and 50% relative humidity and desorption at 90 °C in pure N 2 ). 50TEPA-4.5K/SBA-15 possesses good antioxidation properties; moreover, its CO 2 adsorption capacity stabilizes at 5.45 mmol CO 2 /g adsorbent in 10 consecutive adsorption–desorption cycles, which is much higher than that of 50TEPA/SBA-15 (3.64 mmol CO 2 /g adsorbent ) and also outperforms that of TEPA-functionalized adsorbents in the literature. This study provides new opportunities to develop high-performance solid amine adsorbents for DAC applications.