(273a) Estimation of the Environmental Impacts of [P2228][2-CNPyr] and its Monoethanolamine Based Hybrid Solvent Using Life Cycle Impact Assessment Methodology

Ionic liquids (IL) containing phosphonium cations paired with aprotic heterocyclic anions (AHAs) have shown to be effective in absorbing COâ‚‚, particularly for post combustion processes with significant water concentration. In particular the ionic liquid, triethyl(octyl)phosphine 2-cyanopyrrolide ([P2228][2-CNPyr]), was found to be an ideal candidate to be blended with aqueous monoethanolamine (MEA) as the resulting hybrid solvent showed a significant reduction in the viscosity (compared to neat [P2228][2-CNPyr]) and exhibited a significantly lower the enthalpy of COâ‚‚ desorption (compared to aqueous MEA). Therefore, based on these characteristics, the phosphonium based IL and its corresponding hybrid solvent can be considered as a greener alternative to MEA. However, the available literature on the Lifecycle Assessment (LCA) of phosphonium based ILs suggest the contrary. These studies find that the synthesis route currently being employed to produce the phosphonium cation utilize phosphine and phosgene as precursors which greatly diminish the environmental feasibility of phosphonium based ionic liquids. Therefore, this work suggests an alternate phosphine and phosgene free synthesis route and studies the environmental impacts for producing 1kg of [P2228][2-CNPyr] and its corresponding hybrid solvent mixture with aqueous MEA through this synthesis route. The impacts were estimated based on the Tool for Reduction and Assessment of Chemicals and other environmental Impacts 2.1 (TRACI 2.1) methodology using GaBi LCA Software by Sphera®. This study takes into consideration the various precursors/intermediates in the synthesis route for the production of the two solvents. The TRACI 2.1 methodology was chosen as it calculates the impact of the over ten environmental categories for a holistic environmental impact assessment. This study found that the altered synthesis route could produce the IL and its corresponding hybrid solvent with a lower overall environmental impact than that of MEA. In fact, in this study, both the solvents exhibited lower environmental impacts in 6 and 7 of the 10 environmental categories respectfully when compared to MEA. The study also finds that despite the overall lower environmental impacts of the two solvents, the phosphonium cation synthesis route still remained as a major environmental hotspot. The majority of the environmental impacts was due to the electricity requirement in the IL synthesis route and the material precursors were found to have a lower impact on the environment than that of the electricity requirement in this route. This trend was found to be similar for the production route of both the solvents. Overall, this study found that adopting phosgene and phosphine free synthesis route to produce the phosphonium cation made both the solvents more environmentally sustainable than MEA. Therefore, the authors of this study promote the exploration of alternative, green chemistry synthesis routes for economical and environmentally sustainable IL based COâ‚‚ capture solvents.