Infinite dilution activity coefficient and vapour liquid equilibrium measurements for dimethylsulphide and tetrahydrothiophene with hydrocarbons

The activity coefficients at infinite dilution (γ∞) of dimethylsulphide (DMS) in four hydrocarbon solvents were measured using the dilutor technique at temperatures between 288 K and 303 K. The four hydrocarbons were hexane, 1-hexene, 2,2,4-trimethylpentane and 2,4,4-trimethyl-1-pentene. The dilutor technique is based on the stripping of the highly diluted solute, i.e. DMS, by a constant flow of inert gas. The gas composition was analysed by gas chromatography and the rate of solute removal was calculated from the area of the peaks.In addition, a static total pressure apparatus was used to measure the vapour–liquid equilibrium of the binary systems of propane + DMS and propane + tetrahydrothiophene at 293 K and 313 K. In the static total pressure method, the analysis of the constituent phases is avoided. The systems’ components were injected to the equilibrium cell in known amounts. The composition of the liquid and vapour phase was calculated from the measured temperature and total pressure. The parameters for the Wilson activity coefficient model were regressed. When possible, a comparison between our experimental results and data found in the literature was performed.