The Highly Efficient Absorption of CO2 by a Novel DBU Based Ionic Liquid

Abstract A novel anion-functionalized protic ionic liquid (IL), [DBUH][Triz], has been synthesized from 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) and 1,2,4-triazole (Triz). Density ( ρ ) and viscosity ( η ) of [DBUH][Triz] at different temperatures have been measured and the influence of temperature has been analyzed quantitatively. Then, the applications of [DBUH][Triz] in CO 2 absorption have been investigated. It has been detected that this ionic liquid, which was easily prepared, shows excellent reversibility and a high absorption capacity, about 1.5 mol CO 2 per 1 mol of IL (about 0.3 g CO 2 per 1 g of IL). In addition, the influence of temperature, pressure and moisture on the absorption performance of [DBUH][Triz] has been studied separately, indicating that absorption is promoted by lower temperature and higher CO 2 pressure. In addition, the mechanism of chemical absorption at two active sites has been deduced based on quantum-chemical calculations and 13 C NMR spectra coupled with IR spectra. Furthermore, the equilibrium constant of chemical absorption ( K ) was calculated from the CO 2 capacity at different temperatures ( T ) and a good linear relationship between the natural logarithm of the equilibrium constant ln K and 1/ T was obtained with R 2 of 0.996. From the slope and intercept of the fitted straight line, the molar reaction enthalpy change (Δ r H m ) and molar reaction entropy change (Δ r S m ) were analyzed, indicating that the capture of CO 2 is an exothermic process and the IL–CO 2 complex is less ordered than the pure ionic liquid. Graphic Abstract