Enhancement of CO2 capture performance of aqueous MEA by mixing with [NH2e-mim][BF4]

Abstract

Alcohol amine solutions have a high absorption capacity and rate for CO₂ capture, however, there are some shortcomings such as high energy-consumption and low stability. To enhance CO₂ capture performance of aqueous MEA, a functional ionic liquid ([NH₂e-mim][BF₄]) was introduced based on the advantages for CO₂ capture. Absorbents were prepared with the molar concentration ratio of [NH₂e-mim][BF₄] to the 30 vol% aqueous MEA of 0 : 10, 1 : 9, 2 : 8, 3 : 7, 4 : 6 and 6 : 4. The density and the viscosity of the investigated absorbents were measured and the effects of the molar fraction of [NH₂e-mim][BF₄] (n_I) and temperature on CO₂ absorption performance were investigated. CO₂ desorption performance of the solvent at different temperatures was discussed. The stability performance of the absorbent with n_I of 2 : 8 (I/M_2:8) was examined by five consecutive cyclic tests. The results showed that for pure CO₂, the I/M_2:8 displayed the highest absorption performance at 303 K under 1 bar: a comparable CO₂ absorption capacity of the 30 vol% aqueous MEA and a higher CO₂ absorption rate at the later absorption stage. Moreover, with the increase of temperature, CO₂ absorption capacity and rate decreased, while CO₂ desorption efficiency and rate increased. 393 K was chosen as the optimum desorption temperature with the desorption efficiency of 99.31%. The introducing of IL contributed to CO₂ desorption performance of the absorbents significantly. The properties (CO₂ absorption capacity, mass loss, density and viscosity) of the I/M_2:8 during the cycles suggested that the IL-MEA mixture had an excellent stability performance.