This present work highlights the impact of ammonium-based ionic liquid tetramethylammonium hydroxide (TMAOH) on the formation kinetics of carbon dioxide (CO2), methane (CH4), and their binary mixed gas (50–50 mole%) hydrates. The TMAOH (IL) is applied in varying concentrations (0.5, 1, and 2 wt%) at different experimental temperatures, i.e., 1 and 4°C. The kinetic experiments are conducted in a high-pressure reactor equipped with two-bladed impeller, to provide sufficient agitation. The experimental pressures of CO2, CH4, and mixed 50% CO2 + 50% CH4 were 3.50, 8.0, and 6.50 MPa, respectively. Induction time, the initial apparent rate of formation and the total gas consumed are the kinetic parameters used to evaluate the performance of TMAOH as KHI. The results are further compared with commercial KHI (PVP), at higher subcooling condition of 1°C and 1 wt% of all the studied gaseous systems. Furthermore, the KHI performance of TMAOH is also evaluated via the relative inhibition performance (RIP) compared with other ILs for CO2 and CH4 hydrates. Results revealed that TMAOH delays the induction time for all the considered systems. The presence of TMAOH also reduced the total gas consumed and the initial rate of hydrate formation in most of the studied systems.
Part of the book: Recent Advances in Ionic Liquids
Ionic liquids (ILs) due to their potential dual functionality to shift hydrate equilibrium curve and retard hydrate nucleation are considered as a very promising gas hydrate inhibitor. However, experimental testing alone is insufficient to examine all potential ILs combinations due to a high number of cation and anion to form ILs. In this context, four fundamental properties of IL-hydrate system, namely, sigma profile, hydrogen bonding energies, activity coefficient, and solubility, were stimulated through conductor-like screening model for real solvent (COSMO-RS). ILs were then analyzed to determine if they can be correlated with IL inhibition ability. Among them, sigma profile and hydrogen bonding energies, which later upgraded to total interaction energies, exhibit a significant relationship with IL inhibition ability. Total interaction energies of ions, on the other hand, have successfully been applied to develop a model. The model can predict the thermodynamic inhibition ability in terms of average temperature depression. The correlation was further validated with experimental values from literature with an average error of 20.49%. Finally, using sigma profile graph and developed correlation, the inhibition ability of 20 ammonium-based ILs (AILs) have been predicted. Tetramethylammonium hydroxide (TMA-OH), due to its short alkyl chain length cation and highly electronegative anion, has shown the most promising inhibition ability among the considered system.