IDENTIFICATION OF PRODUCTS RESULTING FROM CARBONYL SULFIDE-INDUCED DEGRADATION OF DIETHANOLAMINE

The degradation of aqueous diethanolamine (DEA) solutions due to carbonyl sulphide (COS) was studied by contacting the solutions (10-40 wt. %) in a well stirred, 600-ml stainless-steel autoclave with COS-nitrogen mixtures at temperatures ranging from 120 to 180-degrees-C. Combined gas chromatography-mass spectrometry, melting point determinations and elemental and infrared analyses were used to identify most of the major reaction products, viz., monoethanolamine, ethylaminoethanol, ethyldiethanolamine, hydroxyethylacetamide, hydroxyethylpiperazine, ethanethioic acid S-hydroxyethylaminomethyl ester, bis(hydroxyethyl)ethylenediamine, bis(hydroxyethyl)piperazine, hydroxyethyloxazolidone, hydroxyethylimidazolidone, tris(hydroxyethyl)ethylenediamine, bis(hydroxyethyl)imidazolidone, acetaldehyde, acetone, butanone, acetic acid, ethanol, diethyl disulphide, dithiane and pyridines. In addition, a solid product containing sulphur was formed. The practical implications of the studies for gas plant operators are discussed.