Enhancing CO2 hydrate kinetics with cost-effective calcium-based montmorillonite for carbon capture
摘要
CO2 emission-driven climate change demands efficient CCUS technology. Montmorillonite (mmt) is an abundant, cheap, and eco-friendly terrestrial porous material, with the potential to turn from a passive geological medium to an active functional material for carbon capture. However, hydrate-based CO2 capture, though promising for high storage density and eco-friendliness, is hindered by slow kinetics and high energy use. To address this, our study systematically explores the enhancement of CO2 hydrate kinetics using mmt through both external optimization and intrinsic modification, by considering the effect of mmt concentration, SDS compounding, stirring rate, comparison with illite, and acid-leached modification. Results indicate that (i) mmt suspensions promote both the CO2 hydrate nucleation and growth, particularly with low concentration, while the enhancement of mass transfer is crucial for the high concentration-mmt system. (ii) Subsequently, the addition of SDS (≥ 1000 ppm) can form micelles to enrich aqueous CO2 locally, and the application of stirring (600 rpm) disrupted hydrate films to enable continuous CO2 supply, which has both proved effective to promote CO2 capture. (iii) The non-expandable illite performed worse than mmt, highlighting the expandable layers and high specific surface area for enhancing hydrate kinetics. This is further verified by acid leaching modification of mmt (m-mmt) that transforms its structure into a highly porous amorphous network. Notably, 1 wt% m-mmt achieved a CO2 capture capacity of 93.9 mmol/mol, representing an 83.9% improvement over pristine mmt. These findings demonstrate the promising promotion effect of mmt for CO2 hydrate, offering new insights for advancing cost-effective hydrate-based CO2 capture.
Graphical Abstract