Ionic liquids tailored amine aqueous solution for pre-combustion CO2 capture: Role of imidazolium-based ionic liquids

The desirable properties of room temperature ionic liquid (RTIL) with low heat capacity, low corrosive, nonvolatile and good CO2 solubility make it possible to tailor the amine aqueous solution for capture of CO2 with low energy consumption. However, the detailed thermal analysis, which is helpful for understanding deeply the energy saving potential for ionic liquids (ILs)-based solvent, is scant. In this work, three different ILs with the same cation, 1-butyl-3-methylimidazolium ([Bmim]), and different anions, including tetrafluoroborate ([BF4]), nitrate ([NO3]), chloride ([Cl]), are used to tailor the N-methyldieth anolamine/piperazine (MDEA/PZ) aqueous solution to assess their role in CO2 capture performance. The results showed that the investigated ILs affect the physical solubility of CO2. Adding [Bmim][BE4] into MDEA/PZ showed the largest CO2 cyclic capacities, whereas, it is the smallest for MDEA/PZ/[Bmim][NO3], which indicates that anion species of the ILs could tune the sensible heat. Based on the calorimeter measured results and modeling estimated results, the reaction enthalpy changes with the addition of different ILs were also observed. The addition of [Bmim][BF4] could reduce the average enthalpy of CO2 dissolution and the sensible heat at 313 K by 30.1% and 20.3%, respectively. Finally, the studies revealed that not only the latent heat of vaporization but also the sensible heat and reaction heat of CO2 capture can be tailored by the choice of ILs. (C) 2015 Elsevier Ltd. All rights reserved.