Wetted-wall column study on CO₂ absorption kinetics enhancement by additive of nanoparticles

Nanoparticles suspended in solutions are considered to have the potential to enhance gas-liquid mass transfer and have been studied for gas separation. In order to reveal the mechanisms of kinetics enhancement, the diffusion and reaction process should be carefully examined. In this paper, CO₂ absorption kinetics of amine-based solutions with additive of SiO₂ and Al₂O₃ nanoparticles were investigated by wetted-wall column experiments. Measurements at different conditions, including solid loading, pressure, and solvent flow rate, show a significant enhancement on CO₂ absorption kinetics. The experiment and model analysis indicate that the micro convective motion induced by particle Brownian movement plays a primary role in mass transfer enhancement. Three solutions, MEA, MDEA, and PZ which have different kinetics were selected to study the impact of nanoparticles on absorption kinetics of solutions with different reaction rate. It is interesting to find that the increased ratio of absorption kinetics by nanoparticle follows the same order with increased solvent reaction rate with CO₂, which is PZ > MEA > MDEA. The wetted-wall kinetic model indicates that a diffusion controlled kinetics for PZ solution could result in much more significant kinetic enhancement with additives of nanoparticles. By operation conditions optimization, the liquid side mass transfer rate of MEA solution can be increased over 15%.