Investigating the Effect of NO on the Capture of CO2 Using Superbase Ionic Liquids for Flue Gas Applications

The effect of acidic gases present in flue gas,
specifically NO, on the capture of CO2 by the superbase ionic
liquid, trihexyltetradecylphosphonium benzimidazolide
([P66614][Benzim]), is reported. An online mass spectrometry
technique was utilized to study the CO2 uptake of the ionic
liquid during multiple absorption and desorption cycles of a
gas feed containing NO and CO2 at realistic flue gas
concentrations, and it was found that while NO alone could
bind irreversibly, the CO2 capacity of the IL was largely
unaffected by the presence of NO in a cofeed of the gases. In
situ attenuated total reflection infrared was employed to probe
the competitive absorption of CO2 and NO by [P66614]-
[Benzim], in which carbamate and NONOate species were
observed to cobind to different sites of the benzimidazolide
anion. These effects were further characterized by analyzing changes in physical properties (viscosity and nitrogen content) and
other spectroscopic changes (1
H NMR, 13C NMR and XPS). Density functional theory computations were used to calculate
binding energies and infrared frequencies of the absorption products, which were shown to corroborate the results and explain
the reaction pathways.