Density and viscosity of aqueous blend of 1-butyl-3-methylimidazolium tetrafluoroburate ([Bmim][BF4]) + piperazine (PZ) and its performance of CO2 absorption

An aqueous blend of 1-butyl-3-methylimidazolium tetrafluoroburate ([Bmim][BF4]) + piperazine (PZ) was proposed in this work. Density and viscosity of the aqueous blend were measured and correlated at (293.15–333.15) K and atmospheric pressure. Performance of CO2 absorption into the aqueous blend was evaluated. It turned out that PZ mass fraction slightly influenced on the density and viscosity, being linear with them. Temperature significantly affected the viscosity. The calculated values are in good agreement with the experimental values. The main factors affecting the CO2 loading of the aqueous blend were PZ mass fraction, gas CO2 mole fraction and temperature. The average absorption rate of the aqueous blend was the biggest in the aqueous [Bmim][BF4], PZ and [Bmim][BF4]/PZ, and much higher than that of the former two. The performance of the aqueous [Bmim][BF4]/PZ with low PZ mass fraction was better than that with high PZ mass fraction. It demonstrated that the aqueous blend of [Bmim][BF4]/PZ is a good absorbent of CO2.