Thermal Stability Of DMSO And Vapor Liquid Equilibrium Of DMSO Aqueous Solution

DMSO (Dimethyl Sulfoxide) is an important chemical and solvent. It has been commercially used in the spinning process of carbon fiber production due to its excellent dissolving ability for polymers. In this process, pure DMSO is obtained by rectification of DMSO-H2O solution. However, DMSO tends to decompose at high temperature, resulting in environmental pollution. In this paper, other separation method of DMSO-H2O was studied. We found a substance which can significantly improve the thermal stability of DMSO, and then measured the vapor-liquid equilibrium of several systems involving DMSO, water and DMF. The main work of this thesis is as follows.Firstly, we measured the liquid-liquid equilibrium data and studied the possibility of using chloroform as extractant for the separation of DMSO-H2O solution. The results showed that chloroform is not feasible for the separation of DMSO-water mixture via extraction due to the low distribution coefficient of DMSO between chloroform phase and water phase.Secondly, we studied the influence of several additives on the thermal stability of DMSO-H2O solution, detected the decomposition products by GC-MS technology, and analyzed the decomposition rate of DMSO by HPLC method. The results showed that DMF has the best effect on enhancing the thermal stability of DMSO-H2O solution, and the stability of DMSO is triplly increased by adding DMF to the solution in an amount of DMF/DMSO=0.01 (mass fraction) in comparison with the contrast solution.And finally, vapor pressure data of binary and ternary systems of DMSO-DMF, DMSO-H2O, and DMSO-DMF-H2O were measured at varying temperatures and concentrations using a quasi-static ebulliometer method. The binary experimental data were correlated by NRTL model, and the resulting binary parameters were used to predict the vapor pressure data for ternary system with good accuracy. It is showed that the addition of small amount of DMF has little influence on the VLE of DMSO-H2O system, implying its negligible effect on the distillation separation of DMSO-H2O mixture. Hence, DMF might be utilized as a stabilizer in DMSO solution in the process of carbon fiber production.