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

Abstract The phase equilibrium conditions of CO 2 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 BF 4 − .