Measurement of the three-phase (vapour + liquid + solid) equilibrium conditions of semi-clathrates formed from mixtures of CO2, CO and H2

Semi-clathrates were formed in an isochoric equilibrium-cell, from gaseous mixtures of (CO2 + H2 + CO), in aqueous solutions of tetra-butyl ammonium bromide (TBAB). The experimental temperatures ranged between (282 and 291) K, experimental pressures ranged between (2.6 and 6.6) MPa and the experiments were conducted in aqueous TBAB solutions of wTBAB = (0.05, 0.10, and 0.20). The gas phase composition was analysed, using gas chromatography, and it was observed that the amount of CO2 in the gas phase was reduced. Additionally, the experimental results were compared to the formation conditions required for gas hydrates, that are formed from the same gas mixtures, and it was observed that the pressure required for semi-clathrate formation was significantly less than that required for gas hydrate formation.

► Equilibrium data for TBAB semi-clathrates formed from gas mixtures of CO2/H2/CO.
► Isochoric technique was used for determining the equilibrium point.
► TBAB solutions were of 5 wt%, 10 wt% and 20 wt%.
► At equilibrium point, a gas phase analysis was conducted using a gas chromatograph.
► The amount of CO2 in the gas phase decreased during the experiment.