CO2 Capture in Wet and Dry Superbase Ionic Liquids

Abstract

The solubility of carbon dioxide (CO2) in five tetraalkylphosphonium superbase ionic liquids, namely the trihexyltetradecylphoshonium phenoxide, trihexyltetradecylphoshonium benzotriazolide, trihexyltetradecylphoshonium benzimidazolide, trihexyltetradecylphoshonium 1,2,3-triazolide and trihexyltetradecylphoshonium 1,2,4triazolide was studied experimentally under dry and wet conditions at 22 °C and at atmospheric pressure using a gravimetric saturation technique. The effects of anion structure and of the presence or absence of water in solution on the carbon dioxide solubility were then deduced from the data. 1 H and 13 C-NMR spectroscopy and ab initio calculations were also conducted to probe the interactions in these solutions, as carbon dioxide and water can compete in the ionic liquid structure during the absorption process. Additionally, the viscosity of selected superbase ionic liquids was measured under dry and wet conditions in the presence or absence of CO2 to evaluate their practical application in carbon dioxide capture processes. Finally, the recyclability of the trihexyltetradecylphoshonium 1,2,4-triazolide under dry and wet conditions was determined to probe the ability of selected solvents to solubilize chemically a high concentration of carbon dioxide and then release it within a low energy demand process.

The addition of CO2to four superbase ionic liquids: a DFT study

“…Calculated enthalpies and geometric parameters for the carbamates and CO 2 adducts are reported in Table 6 To get an energetic explanation of this important modification caused by the cation, the ionic pairing energy, ∆E IPCO2 , was calculated for the ionic pair-carbamate products (Table 7). However, it is still consistent with the experimentally observed molar absorption capacities 14 (Table 7). For each separate anion, the most favourable carbamate is the one with the strongest resulting ionic pair.…”

“…Comparison of CO 2 addition enthalpies (kJ mol -1 ) for the four anions from the anion-only model, plotted against experimental CO 2 uptake from reference [14]. Comparison of CO 2 addition enthalpies (kJ mol -1 ) for the four anions from the anion-only model, plotted against experimental CO 2 uptake from reference [14].…”

“…In the same year, Taylor et al determined the absorption capacities for four superbase ionic liquids (SBILs) ( Table 1) 14 . Absorption capacity was determined under both dry and wet conditions.…”

Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid

“…In these systems, [P 66614 ][124Triz], for example, has been shown to absorb equimolar quantities of CO 2 through the chemical interaction of CO 2 with the anion and physical absorption of CO 2 in the solution free space (Scheme 1). [6b, 17] This set of ILs have been studied extensively for CO 2 capture but, to date, no reports of their use in CO 2 conversion have been published. A key feature of the anion–CO 2 interaction is that the CO 2 chemically binds without prior reduction to [ .…”

Halogen free 1,2,3- and 1,2,4-triazolide based ionic liquids: synthesis and properties

“…As a result of the low acidity of 1,2,4-and 1,2,3-triazoles, their corresponding anions are considered to be superbases, 16 and several 1,2,3-triazolide ILs were used for CO 2 capture 17 and CO 2 electrochemical reduction. [18][19][20] The triazole-1,2,4-ide anion was employed as a part of highly energetic ILs as well. 21 However, their electrochemical properties remain unexplored.…”