Carbon Dioxide Capture Emulsions Enable High-Rate Absorption in a High-Capacity Tertiary Amine

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.