Alkanolamine-based carbon capture solvents face a fundamental compromise: widely used primary and secondary alkanolamines such as monoethanolamine absorb CO2 rapidly but are stoichiometrically limited by carbamate formation, whereas tertiary alkanolamines such as N-methyldiethanolamine (MDEA) offer higher capacity but slow absorption rates. We present a CO2 capture fluid architecture that overcomes this compromise for MDEA by removing its mass-transfer limitation. We encapsulate the aqueous MDEA solution in droplets within a continuous CO2 carrier phase and render the emulsion stable with surface-active silica nanoparticles. The resulting triphase fluid achieved interfacial area-to-volume ratios on the order of 106 m2/m3, enabling a 6-fold enhancement in absorption rate. This enhancement persisted under industrially relevant conditions, including dilute CO2 streams (14%) and wet gas exposure. The emulsion maintained stable absorption capacity over 10 successive cycles and demonstrated no foam formation during operation. This approach is also compatible with alternative low-volatility carrier fluids (decane, dodecane). Emulsification preserves the high capacity of MDEA while circumventing the absorption rate limitation that has hindered their application in carbon capture to date.
Saber et al. (Fri,) studied this question.