Enhanced gravimetric CO2 capacity and viscosity for ionic liquids with cyanopyrrolide anion

Ionic Liquids (ILs) are considered as alternative solvents for the separation of CO₂ from flue gas due mainly to their CO₂ affinity and thermal stability. The cation architecture in a matrix of ammonium and mostly phosphonium‐based ILs with 2‐cyanopyrrolide as the anion to evaluate its impact on gravimetric CO₂ absorption capacity, viscosity, and thermal stability and the three fundamental properties vital for application realization are systematically investigated. Among the investigated ILs, [P2,2,2,8][2‐CNpyr] demonstrated the lowest viscosity, 95 cP at 40°C, and highest CO₂ uptake, 114 mg CO₂ per g IL at 40°C. Combined effects of asymmetry and the optimized chain lengths also resulted in improved thermal stability for [P2,2,2,8][2‐CNpyr], with a mass loss rate of 1.35 × 10^?6 g h^?1 (0.0067 mass % h^?1) at 80°C. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2280–2285, 2015