Performance and pressure drop of CO2 absorption into task‐specific and halide‐free ionic liquids in a microchannel.

The gas–liquid two‐phase flow pattern, absorption rate and pressure drop of CO2 absorbed into the aqueous solution of the task‐specific ionic liquids (1‐aminopropyl‐3‐methylimidazole tetrafluoroborate [Apmim][BF4] and 1‐hydroxyethyl‐3‐methylimidazole tetrafluoroborate [OHemim][BF4]) and halide‐free ionic liquid 1‐butyl‐3‐methylimidazolium methylsulfate [Bmim][CH3SO4] were investigated in a microreactor. The absorption mechanism of the three ionic liquids was analyzed employing the 13C NMR spectroscopy. The [Apmim][BF4] was found to have the best ability of CO2 capture compared with the other two ionic liquids, as chemical absorption occurred between [Apmim][BF4] and CO2, while only physical absorption took place between [OHemim][BF4]/[Bmim][CH3SO4] and CO2. The sequence of CO2 absorption rate in three ionic liquids aqueous solutions is: [Apmim][BF4] > [Bmim][CH3SO4] > [OHemim][BF4]. Furthermore, the effects of gas–liquid flow rate and ionic liquids concentration on CO2 absorption rate and pressure drop were studied, the pressure drop models based on various flow patterns were proposed. [ABSTRACT FROM AUTHOR]