Thermodynamic inhibition of CO2 hydrate in the presence of morpholinium and piperidinium ionic liquids

The phase equilibrium conditions of CO2 hydrates were examined in the presence of morpholinium and piperidinium ionic liquids (ILs) with a mass fraction of 0.1. The equilibrium conditions were in the ranges of (274.6-281.2) K and (1.80-3.95) MPa. The addition of ILs shifted the hydrate equilibrium conditions to a higher pressure and lower temperature region compared to the hydrate formed from pure water. Piperidinium and morpholinium ILs showed similar inhibition effects in the higher temperature range >= 278.5 K, whereas at lower temperature piperidinium ILs had a slightly better inhibition effect than morpholinium ILs. The anionic species also affected the hydrate inhibition effectiveness. Smaller anions, i.e., Br-, had a slightly better inhibition effect than the bigger ions of UZI. (C) 2015 Elsevier B.V. All rights reserved.