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Accelerated Aging and Qualitative Degradation Pathway Analysis of CO2 Capture Solvents Containing Ionic Liquids

LaFrate, Andrew L., Huffman, Michael C., Brown, Nathan, Shannon, Matthew S., Belmore, Ken, Bara, Jason E.
Energy & Fuels 2012 v.26 no.8 pp. 5345-5349
air, carbon, carbon dioxide, ethanolamine, gas chromatography-mass spectrometry, ionic liquids, nitrogen, oligomerization, sulfur dioxide, temperature
A qualitative study was conducted to analyze degradation of CO₂ capture solvents containing ionic liquids by GC/MS under a variety of conditions representative of the carbon capture process. Aqueous monoethanolamine (MEA) was used as a benchmark for solvent degradation and compared to two advanced CO₂ capture solvents containing ionic liquids. Accelerated aging experiments were conducted in the laboratory by exposing solvents to various gases (N₂, air, CO₂, or SO₂) at elevated temperature in sealed cylinders. Degradation products were analyzed by GC/MS and key pathways leading to their formation were elucidated. For all solvents, degradation was most rapid and lead to a wider array of products in the presence of CO₂ compared to the other studied gases. The ionic liquid solvents showed enhanced degradation and a different set of degradation products than those observed for MEA. In one case, the anion of the ionic liquid was found to be reactive and led to a unique primary degradation mechanism not seen in other solvents. The polar and charged nature of the ionic liquid solvents is also believed to enhance the nucleophilic substitution reaction rates that lead to amine oligomerization degradation products in these types of systems.