Separation of methane-ethylene via forming semi-clathrate hydrates with TBAB

The formation conditions of CH4-C2H4 hydrate in water and 10 wt% tetra-n-butyl ammonium bromide (TBAB) solution were measured in this work. On this basis, the equilibrium separation of CH4-C2H4 via TBAB semi-clathrate hydrate formation was conducted at constant temperature and pressure. The results show that the influence of TBAB on the formation of CH4-C2H4 hydrate changes with temperature. At low temperature, TBAB forms semi-clathrate hydrate and acts as a promoter for CH4-C2H4 hydrate. At high temperature, TBAB exists as a salt compound and behaves as an inhibitor for CH4-C2H4 hydrate. CH4-C2H4 can be efficiently separated via TBAB semi-clathrate hydrate formation under proper temperature and pressure. The results indicate that C2H4 can not be encased in the dodecahedral cages of TBAB hydrate. Therefore, the concentration of C2H4 in hydrate could be as low as 0.55 mol% and the recovery of C2H4 could reach 99.85% in equilibrium gas.