Kinetics of CO2 capture by ionic liquid—CO2 binding organic liquid dual systems

• A dual system, consisting of [bmim][Tf2N] and DBU in 1-hexanol medium has been developed for CO2 capture.
• Intrinsic reaction rate of this system -measured by a stopped flow technique- follows termolecular reaction mechanism.
• The developed solvent has a high CO2 loading capacity and favorable reaction kinetics.
• Activation energy of the reaction between the dual system and CO2 was found to be 55.62 kJ/mol.
• FITR studies showed that the loaded solvent can be regenerated at 363 K without a reboiler requirement.

A dual system, which aims to combine the individual advantages of two different solvents, has been developed for CO2 capture in order to intensify the process by reducing the reboiler duty. The dual system consisted of 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) and 1.8-diazabicyclo 5.4.0 undec-7-ene (DBU) in 1-hexanol medium and the relevant kinetics were determined by using a stopped flow equipment. Based on pseudo-first-order reaction kinetics of CO2, the reaction was modeled by a modified termolecular reaction mechanism and rate constants and the activation energies of the [bmim][Tf2N]–DBU system were obtained. In addition, the absorption capacity and the initial absorption rate of the 10 wt% [bmim][Tf2N]-15 wt% DBU dual system were measured in a gas-liquid reactor at 303 K and 2 atm 0.815:1 mol ratio of CO2:DBU was achieved with this dual system – which approximately doubles the capacity of commercial alkanolamine solutions – and the initial CO2 absorption rate of the dual system was found to be 3.500 × 10−5 kmol/m2s. Reversibility of dual system was also briefly investigated by using Fourier transform infrared spectrometry.