Assessing IoliLyte® ionic liquids potential as gas hydrate inhibitors: thermodynamics, kinetics and toxicity evaluation

The inhibition of gas hydrates is a critical challenge for the petrochemical industry, particularly for flow assurance in deep-sea pipelines. This study investigates the potential of three commercial ionic liquids (ILs) from the IoliLyte® family—T2EG, C1EG, and 221PG— as hydrate inhibitors. The phase behaviour of CO₂ hydrates in the presence of different IL concentrations (10 wt%–40 wt%) was analyzed using an isochoric pressure search method within temperature and pressure ranges of 3 °C–9 °C and 16 bar–37 bar, respectively. While T2EG and C1EG exhibited no effect on the hydrate equilibrium, 221PG acted as a thermodynamic hydrate inhibitor (THI), shifting the equilibrium curve in a concentration-dependent manner. Additionally, the kinetic inhibition efficiency was evaluated (0.1 wt%–1 wt%) using a constant cooling ramp method at 30 bar, revealing a decrease in the onset nucleation temperatures and reduction in pressure drops, indicating delayed nucleation and inhibited hydrate growth. The ILs were further tested for their influence on tetrahydrofuran (THF) hydrate dissociation at atmospheric pressure using differential scanning calorimetry (DSC), which qualitatively indicates thermodynamic inhibition of sII hydrates. The physicochemical properties of ILs, including density, viscosity, speed of sound, and refractive index, were measured at different temperatures, and the thermal characterization was performed via DSC. Finally, the microbial and the acute toxicity were assessed through minimum inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and zebra fish embryo tests (ZFET) to evaluate their suitability for deep-sea applications. Among the tested ILs, 221PG emerged as the most promising, displaying both thermodynamic and kinetic inhibition capabilities for CO₂ hydrates, while also being the most environmentally benign option.