Solubilities of CO2 in, and Densities and Viscosities of, the Piperazine+1-Ethyl-3-methyl-imidazolium Acetate + H2O System

Densities and viscosities of hybrid absorbents piperazine (PZ) (1) + 1-ethyl-3-methyl-imidazolium acetate ([Emim][Ac]) (2) + H2O (3) were respectively measured with different mass compositions (w(1)/w(2)/w(3) = 0.3/0/0.7, 0.3/0.1/0.6, 0.3/0.2/0.5, 0.3/0.3/0.4, 0.2/0.3/0.5, 0.1/0.3/0.6, 0/0.3/0.7) at temperatures ranging from 313.15 K to 343.15 K, and correlated with proper models. The density declines slightly while the viscosity decreases greatly with the increase of temperature. It is effective to lessen the viscosities of hybrid absorbents as the increase of [Emim][Ac] concentration and decrease of PZ concentration with constant water content, and densities are vice versa. Solubilities of CO2 in hybrid absorbents at T = 313.15 K to 343.15 K were measured by using an isothermal synthetic method under pressures of 0 MPa to 1.0 MPa. The results show that solubilities ascend with a decrease of temperature and increase of pressure. The addition of PZ highly improves the absorption ability of hybrid absorbent, while [Emim][Ac] has little effect on the CO2 absorption ability of a highly concentrated PZ aqueous solution. Furthermore, CO2 loading of 0.3 PZ + 0.1 [Emim] [Ac] + 0.6 H2O is superior when it is compared with literature data, showing it is a potential CO2 absorbent deserving further research. The viscosity of the hybrid absorbent is much lower than that of pure [Emim][Ac] which improves the practical significance of hybrid absorbents.