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 (1H 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