Alkanolamines are exclusively used as chemical solvents for absorbing acid gases like CO2, H2S and other sulfur species in both petroleum refinery and natural gas processing industry. Accurate phase equilibrium data for acid gas and amine aqueous solution systems are necessary for the design and optimization of gas treatment units. Although there are plenty of phase diagram available for main alkanolamines (e.g. MEA, DEA, MDEA) and major acid gases (e.g. CO2, H2S), there is still a need for generating equilibrium data concerning solubility of organic sulfur species e.g. Mercaptans, thiols, carbonyl sulfide (COS) and carbon disulfide (CS2) in amine aqueous solutions

In this work, new experimental data for partition coefficients of n-Propylmercaptan, n-Butylmercaptan and Dimethylsulfide in (50 wt %) MDEA aqueous solution at 366 K and pressure 6.9 MPa are reported. The concentration of n-Propylmercaptan in aqueous phase is in the (50 – 1000) ppm (mole) range. The data have been generated using a “static-analytic” apparatus which takes advantage of a ROLSITM sampler with a gas chromatograph for components analyzes. Measurements are made for different acid gas loadings and CH4 is used to maintain the total pressure of the system in equilibrium cell. The reactions between organic sulfur species and (MDEA or DEA) aqueous solutions are presented by using acid base neutralization approach. The effect of CH4 partial pressure on partial pressure of acid gas is studied. Partial pressures of CO2 and H2S are plotted as function of acid gas loadings. The effect of acid gas loadings on physical and chemical solubility of n-Propylmercaptan, n-Butylmercaptan and Dimethylsulfide are also discussed.