Degradation of aqueous diethanolamine solutions by carbon disulfide

The degradation of aqueous diethanolamine (DEA) solutions by carbon disulfide (CS₂) was investigated using a batch reactor at temperatures ranging from 120 to 190 °C, DEA concentrations of 2 to 6 M and $\text{CS}{}_2\text{DEA}$ mole ratios of 0.05 to 0.23. Reaction products identified by gas chromatography (GC), gas chromatography/mass spectrometry (GC/MS), melting point determination, elemental analysis and infrared analysis include monoethanolamine, bis(hydroxyethyl)-ethylenediamine, bis(hydroxyethyl)-piperazine, hydroxyethyl-oxazolidone, hydroxyethyl-imidazolidone, tris(hydroxyethyl)-ethylenediamine, bis(hydroxyethyl)-imidazolidone and an insoluble, sulfur-rich, linear, polymeric solid. The formation of the products increased with temperature, DEA concentration and $\text{CS}{}_2\text{DEA}$ mole ratio. A mechanism for the formation of the products is presented, and the experimental data are consistent with a first-order overall reaction with respect to DEA.