Facile Method for Determination of Amine Speciation in CO₂ Capture Solutions

A simple and quantitatively reliable method for determination of amine speciation is introduced. The method employs three experimental methods that should be readily accessible. The results for CO₂ loaded aqueous solutions of 30 wt % monoethanolamine (MEA) are used for demonstration of the method and show promising agreement with the more complicated spectroscopic methods reported in the literature. The measurements were done at ambient temperature and atmospheric pressure, since theoretical calculations and experimental data from the open literature revealed no considerable difference in speciation at different temperatures. The procedure is based on acid and base titration of the CO₂ loaded amine solution along with the determination of total CO₂ loading. The quantitative results for the different species concentration in the example MEA solution is in agreement with other available spectroscopic methods, mainly NMR, particularly for the free amine, carbamate, and protonated amine concentrations. Aspen Plus was also used for further assessment of the experimental data.