(719f) Comparative Microfluidic Screening of Amino Acid Salt Solutions for Post-Combustion CO2 Capture

The CO₂ absorption capacity and rate of the
potassium salts of glycine, taurine, proline, and lysine were compared with MEA
by tracking the volume change of an entrained CO₂ gas plug as it
traveled through a microfluidic channel (see figure 1). The potassium salt of
lysine, which contains two primary amine functional groups, exhibited the
highest rich CO₂ loading, >50% higher than MEA. The salts of
glycine, and taurine exhibited similar absorption capacity to MEA, and the salt
of proline exhibited the lowest absorption capacity (see figure 2). The trend
in absorption capacities of the potassium salt of lysine and MEA was also
observed in a set of breakthrough experiments in a continuously stirred reactor
vessel. Experiments were conducted to compare the CO₂ absorption
capacity on the basis of both constant molar concentration (0.5M) and constant
mass fraction (30%) of the absorbent molecule and the significance of this
difference are highlighted. Specifically, the higher molecular weight of lysine
is identified as a drawback to its use. Raman spectroscopy was used to analyze
the neat absorbent solutions as well as the microfluidic reactor effluent and
spectral features of carbamate, carbonate, and bicarbonate were identified in
the effluent spectra. The effectiveness of the microfluidic reactor as a volume
and time efficient screening tool is demonstrated. The results suggest further
work should be done to evaluate the efficacy of the alkali salt of lysine as a
post-combustion CO₂ capture absorbent as it has potential to match
or possibly improve upon the CO₂ loading of MEA while offering
advantages such as low toxicity and lower volatility.