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Investigation of the Degradation of Aqueous Ethylene Glycol and Propylene Glycol Solutions Using Ion Chromatography.


pdf icon Investigation of the Degradation of Aqueous Ethylene Glycol and Propylene Glycol Solutions Using Ion Chromatography. (1136 K)
Rossiter, W. J., Jr.; Godette, M.; Brown, P. W.; Galuk, K. G.

Solar Energy Materials, Vol. 11, 455-467, 1985.

Keywords:

ethylene glycol; propylene glycol; chromatography; degradation products; thermal oxidation; solar collectors; copper; degradation; metals

Abstract:

Aqueous solutions of ethylene glycol and propylene glycol produce acidic degradation products upon thermal oxidation. This results in a decrease in pH of the aqueous solutions which could accelerate the corrosion of metalllic components of solar collectors. The increase in the concentrations of degradation products in solution was measured over time using the Ion Chromatography Exclusion (ICE) method of analysis. Variables affecting the thermal oxidation considered in the investigation were temperature, the presence of metals and oxidative conditions (aeration/deaeration). Acidic degradation products were produced under all conditions. The presence of metallic copper in aerated glycol solutions resulted in the greatest extent of degradation. Comparisons were made between the pH values of the thermal oxidatively degraded glycol solutions and the concentrations of degradation products. It was found that different solutions having comparable pH values contained significantly different amounts of degradation products. It was concluded that the extent of degradation of the glycol cannot be used as an indicator of the magnitude of the decrease in pH which the glycol solution may undergo during thermal oxidation in the presence of metals.