CO2 absorption in diethanolamine/ionic liquid emulsions – Chemical kinetics and mass transfer study

• Kinetics of diethanolamine (DEA) dispersion in [hmim][Tf2N] for efficient CO2 capture.
• 2-Scale diffusion/reaction model for mass transfer, kinetics and initial DEA droplet size.
• Stoichiometric-maximum gas loading owing to water-free precipitation of CO2-captured product.
• Kinetic model uses zwitterion mechanism for pure DEA dispersed in [hmim][Tf2N] ionic liquid.

CO2 absorption in diethanolamine (DEA)–ionic liquid ([hmim][Tf2N]) blends in a laboratory scale gas–liquid/liquid stirred-cell reactor was studied at various amine concentrations, CO2 partial pressures, agitation speeds, and temperatures. A two-scale, isothermal, unsteady-state model accounting for CO2 diffusion/reaction in amine dispersed droplets was used to simulate the behavior of the gas–liquid/liquid stirred-cell reactor and to evaluate the kinetic and mass transfer parameters and the initial size of the DEA dispersed droplets. The kinetic model used to describe the chemical reaction of CO2 in non-aqueous amines is based on the zwitterion mechanism followed by the removal of a proton by the amine and formation of immiscible solid carbamate crystals in the ionic liquid phase. The gas–liquid/liquid stirred-cell reactor model incorporates gas–liquid mass transfer, liquid–solid–liquid mass transfer, CO2 diffusion in CO2-captured solid carbamate product, and the time evolution of amine droplets size.