A general Energy-Efficient strategy for optimizing CO2 Capture: Designing and harnessing the rapid adsorption kinetics of Amine-Impregnated adsorbents

Abstract

This study aims to optimize the performance of amine-impregnated CO2 adsorbents for both direct air capture (DAC) and point source CO2 capture (PSC) applications. The main objective of this study is to investigate the relationship between the weight fraction of amine loading and the efficiency of CO2 uptake on the designated support, aiming to find a straightforward method to design effective amine support materials. To this end, a composite material denoted as PEI/CNT@ZIF-8 has been developed. This composite is comprised of polyethylenimine (PEI), multi-walled carbon nanotubes (CNTs), and zeolitic imidazolate frameworks (ZIF-8). CNTs offer several advantages for enhancing CO2 uptake, including rearranging the ZIF-8 particles to facilitate PEI loading, creating strong electrostatic interaction for amine anchoring, and establishing CO2 diffusion channels to improve CO2 capture kinetics. In DAC scenarios, with a CO2 concentration of 400 ppm balanced with N2, the 25.0 wt% PEI/CNT(1)@ZIF-8(5) demonstrates superior CO2 uptake, achieving 4.08 mmol g−1 within a one-hour interval by harnessing the rapid kinetic region and exhibiting a low desorption energy of 55.8 kJ mol−1 for releasing CO2. In PSC scenarios, with a CO2 concentration of 15 vol% under both dry and wet conditions, the 37.5 wt% PEI/CNT(1)@ZIF-8(5) exhibits excellent CO2 uptake of 2.21 and 2.58 mmol g−1, respectively, at 50 ℃. The findings suggest that adjusting the balance between CO2 uptake and adsorption kinetics by considering the amine weight fraction can optimize the performance of solid amine CO2 adsorbents across diverse operational conditions. Furthermore, rather than relying on a single support material, this study reveals the potential of combining CNTs with materials such as SiO2 nanoparticles, Al2O3, or metal–organic frameworks (MOFs) to enhance CO2 capture performance. This approach holds promise as an effective and straightforward strategy.