Highly efficient and reversible CO2 capture through 1,1,3,3-tetramethylguanidinium imidazole ionic liquid

Abstract

1,1,3,3-Tetramethylguanidinium imidazole ([TMG][IM]) ionic liquid was synthesized and its absorption and desorption of CO₂ were investigated, as well as the effect of reaction temperature, N₂, and moisture on capture of CO₂ and the absorption mechanism. The results show that the maximum molar ratio of CO₂ to [TMG][IM] is to achieve 1.01 at 30 °C under atmosphere pressure with a high absorption rate. The capture capability is not obviously affected by the moisture of CO₂, but decreases with temperature increasing from 30 to 50 °C. The absorption mechanism might be that CO₂ reacts with the imidazole anion of [TMG][IM] and then a new carbamate group is formed, which is confirmed by IR and NMR spectra. The enthalpy of CO₂ absorption for [TMG][IM] is −30.3 kJ mol⁻¹. The captured CO₂ can be readily released at 65 °C by bubbling N₂ and recycled with little loss of its capture capability. Considering the efficient and reversible process with [TMG][IM], this method has great potential for the capture of CO₂.