Physicochemical characterization and activity coefficients at infinite dilution of molecular compound in poly(ethylene glycol)dimethyl ether and the eutectic mixture composed of poly(ethylene glycol) with cyclic carbonate

Abstract

This work is focused on determining the effectiveness of using hitherto unexplored extractants in separation processes. It is proposed to use poly(ethylene glycol) and the eutectic mixture composed of poly(ethylene glycol) with cyclic carbonate as separating agents in desulphurization of model fuel (heptane/thiophene) and alkanes from aromatic hydrocarbons (heptane/toluene) processes. The selected glycol was poly(ethylene glycol)dimethyl ether with an average molecular weight of M = 250 g·mol−1 (abbreviated as PEG250DME). The second component of the mixture was ethylene cyclic carbonate (abbreviated as EC). These components create a non-crystallizing mixture at a temperature below T = 203 K in the range of 25–40% ethylene carbonate, thus a mixture with the following composition 30% of EC and 70% of PEG250DME (wEC = 0.331) was investigated. For this purpose, the extensive research on the infinite dilution activity coefficients for 45 molecular compounds including alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, ethers, pyridine, thiophene, acetone, acetonitrile, and 1-nitropropane in both PEG250DME and {[PEG250DME] + [EC], wEC = 0.331} were determined. The experiment was performed at a temperature range from T = (308.15 to 338.15) K with an increment of 10 K using gas–liquid chromatography (GLC). Based on the experimental data, the infinite dilution capacity and selectivity of the PEG250DME and DES: {[PEG250DME] + [EC], wEC = 0.331} are presented to evaluate the effectiveness of using them as an extractant in the separation of aliphatic from aromatic hydrocarbons and sulfur compounds from alkanes. Obtained selectivity and capacity values for different separation processes are compared with the literature data for other separating agents presented in the available literature reports. From the temperature - dependence of the infinite dilution activity coefficient, the partial molar excess Gibbs energy, ΔG1E,∞, enthalpy ΔH1E,∞ and entropy term TrefΔS1E,∞ at infinite dilution were calculated and discussed. Additionally, the liquid density and dynamic viscosity of pure PEG250DME and it’s eutectic mixture with EC as a function of temperature were determined. Both of the physicochemical parameters are important from a technological point of view.