Density, viscosity, and H2S solubility of N-butylmorpholine bromide iron-based ionic liquids

Abstract

The density and viscosity of N-butylmorpholine bromide iron-based ionic liquids (rFeCl3/ [Nbmm]Br) with two iron-morpholine ratios (r = 0.8 and 1.0) mol·mol−1 were measured at 303.15–348.15 K and 101.3 kPa. Density and viscosity data were fitted by empirical correlations for temperature. The average relative errors were less than 0.02 % and 2 %, respectively. The density and viscosity decrease with increasing temperature. The density increases with the increase of r, while the viscosity shows the opposite trend. The gas-liquid equilibrium data of H2S in rFeCl3/[Nbmm]Br were measured by the isochoric pressure drop method at temperatures of 303.15–348.15 K, pressures of 0–200 kPa, and r of 0.8 and 1.0 mol·mol−1. The total solubility of H2S increases with decreasing temperature, increasing pressure, and decreasing r. The measured solubility data were fitted by the reaction equilibrium thermodynamic model. Chemical reaction equilibrium constant and the Henry's constant at different temperatures and different r were obtained. The average relative error of model fitting is less than 3 %. The results show that the chemical reaction equilibrium constant and the Henry’s constant both decrease with the increase of r, and decrease of temperature. Effect of molecular structure on reaction equilibrium constants was explained by quantum chemistry calculation. The absorption of H2S in rFeCl3/ [Nbmm]Br at low pressure is dominated by chemical absorption. With the increase of pressure, the proportion of physical absorption continues to increase, and gradually occupies the main part.