Thermal Degradation of Monoethylene Glycol in Aqueous Saline Solution: Evaluation by Thermogravimetric and Physicochemical Analyses

In order to represent the thermal effects of the operational conditions of a monoethylene glycol (MEG) regeneration unit, 86 wt % MEG aqueous solutions with salt concentrations up to 5.52 wt % were heated for 56 h in an ebulliometer. Seven analytical techniques were applied to the samples, aiming to evaluate MEG degradation. Results demonstrated that increasing the sodium chloride concentration from 0 to 5.52 wt % reduced the MEG thermal stability time from 44 to 8 h. Thermogravimetric analysis was the most adequate studied technique to quantify MEG thermal degradation. Measurements of MEG degradation were correlated, using an allometric expression for each sodium chloride concentration. The salt-free solutions presented 7.2% MEG degradation after 56 h heating, while for 5.52 wt % NaCl it increased to 21.1%. As expected, sodium chloride concentration and time of exposure to temperatures up to 140 °C are important variables for monitoring MEG thermal degradation, especially in the flash evaporator.