Influence of temperature and pressure on the density and speed of sound of 2-hydroxyethylammonium propionate ionic liquid

Abstract

Abstract The alkanolammonium ILs are protic ionic liquids (PILs) with huge potential in a variety of industrial fields. Among other advantages, these PILs have low cost of preparation, simple synthesis and purification methodologies and low toxicity. This study aims at obtaining significant data on the fundamental thermophysical properties of hydroxyethylammonium-based PILs with carboxylate anions. The density was measured within the temperature and pressure intervals (298.15–343.15) K and (0.1–35.0) MPa for 2-hydroxyethylammonium propionate, [2-HEA][Pr]. The speed of sound was determined in the ranges (303.15–353.15) K and (0.1–20.0) MPa for the same substance. The estimated combined standard uncertainties are ±0.45 kg·m−3 for density and ±1.6 m·s−1 for speed of sound. The experimental pVT data were fitted using the Goharshadi–Morsali-Abbaspour equation of state (GMA EoS) with average relative absolute deviation (%AARD) of 0.03%. Thermomechanical coefficients as the thermal expansivity, isothermal compressibility, and internal pressure, were calculated using GMA EoS with the internal pressure being further compared with calculated values of cohesive energy density. The experimental pVT data were further successfully described by the predictive methods of Gardas and Coutinho and Paduszynki and Domanska.