CO2 absorption by biphasic solvents: Comparison with lower phase alone

Abstract

The mixtures of 2 M 1,4-butanediamine (BDA) and 4 M 2-(diethylamino)-ethanol (DEEA) have been found to be promising biphasic solvents. This work identifies the composition of the lower phase using a DX-120 Ion Chromatograph (IC) and a Metrohm 809 Titrando auto titrator. The cyclic capacities, cyclic loadings and reaction products of the biphasic solvent are compared with those of the aqueous solution with the same amine concentration as the lower phase of the biphasic solvent at the rich loading ((2B4D)L) using a fast screening facility and a JNM ECA-600 Nuclear Magnetic Resonance spectrometer (NMR). Their absorption rates at different loadings are also investigated using a Wetted Wall Column (WWC). The results show that the cyclic capacity and cyclic loading of (2B4D)L are almost the same as those of 2B4D. The absorption rate of (2B4D)L is higher than 2B4D at all the 3 tested loadings, except for the fresh solutions at CO2 pressure lower than 10 kPa. NMR results show that the reaction products of (2B4D)L had more BDA bicarbamate, less BDA and less BDA carbamate than 2B4D. The CO2 reaction products of (2B4D)L had twice as much carbonate/bicarbonate as with 2B4D and less BDA carbamate.