Hydrate Phase Equilibria of Ternary Gas Mixtures with Tetrabutylammonium Bromide and Cyclopentane

As unconventional natural gas and hydrate-based gas separation (HBGS) technology has attracted increasing attention, the safe and effective improvement of the reaction rate and separation effect of hydrates has also become the focus of extensive research. Tetrabutylammonium bromide (TBAB) and cyclopentane (CP) are common thermodynamic additives for promoting hydrate formation. To determine the effect of additives on the hydrate phase equilibria of multicomponent gas, the hydrate phase equilibrium conditions of a synthetic ternary gas mixture (CH4/CO2/N-2 = 0.5/0.4/0.1) were investigated in a solution prepared using CP and different concentrations of TBAB aqueous solutions (0.05, 0.1, 0.2, and 0.4 mass fractions) with a volume ratio of 0.308 (V/V). The promotion effect of the additives on mixed gas hydrate was weaker than that of pure CP, and the concentration of TBAB had a significant effect on the hydrate phase equilibrium of the system. The effect of TBAB could be neglected at a TBAB mass fraction of 0.05, and that of CP could be neglected at a TBAB mass fraction of 0.4. The results provide theoretical support for the HBGS technology.