Application potential of N-hexylpyridinium bromide for separation azeotrope: Thermodynamic properties measurements

Abstract

• The thermodynamic behavior of [Hpy]Br was measured by IGC technology. • Obtained the VLE data of [Hpy]Br with solvents and correlated with the NRTL. • The potential of [Hpy]Br as an extractive distillation entrainer was evaluated. A series of thermodynamic parameters of N-hexylpyridinium bromide ([Hpy]Br) ionic liquid (IL) were investigated by inverse gas chromatography (IGC) technique. These parameters included the Flory-Huggins interaction parameters ( χ 12 ), activity coefficients at infinite dilution ( γ 12 ∞ ), molar heat (enthalpy) of probe absorption in the [Hpy]Br ( Δ H 1 S ), molar heat of mixing at infinite dilution between [Hpy]Br and probe ( Δ H 1 ∞ ), and Hildebrand solubility parameters ( δ 2 ). The isothermal vapor-liquid equilibrium (VLE) data of [Hpy]Br and solvents with good solubility at 353.15K were determined from χ 12 and correlated with the NRTL model. The potential of [Hpy]Br as an entrainer for separating benzene (1)/ethanol (2), benzene (1)/isopropanol (2), and benzene (1)/thiophene (2) azeotropic mixture by extractive distillation was explored using the y - x ′ diagram. Results showed that the azeotropy of three binary systems could be broken by adding [Hpy]Br and the reliability of thermodynamic analyses was verified.