Phase equilibrium conditions for simulated landfill gas hydrate formation in aqueous solutions of tetrabutylammonium nitrate

• Hydrate equilibrium conditions for the simulated landfill gas (LFG) were reported.
• Thermodynamic effect of tetrabutylammonium nitrate changes with its mass fraction.
• The phase boundary was determined by employing an isochoric pressure-search method.

Hydrate phase equilibrium conditions for the simulated landfill gas (LFG) of methane and carbon dioxide (50 mol% methane, 50 mol% carbon dioxide) were investigated with the pressure range of (1.90 to 13.83) MPa and temperature range of (280.0 to 288.3) K at (0.050, 0.170, 0.340, and 0.394) mass fraction (w) of tetrabutylammonium nitrate (TBANO3). The phase boundary between liquid–vapor–hydrate (L–V–H) phases and liquid–vapor (L–V) phases was determined by employing an isochoric pressure-search method. The phase equilibrium data measured showed that TBANO3 appeared a remarkable promotion effect at wTBANO3wTBANO3 = 0.394, corresponding to TBANO3 · 26H2O, but inhibition effect at wTBANO3wTBANO3 = (0.050, or 0.170) on the semiclathrate hydrate formation. In addition, the application of TBANO3 at 0.340 mass fraction, corresponding to TBANO3 · 32H2O, displayed promotion effect at lower pressures (below 6.38 MPa) and inhibition effect at higher pressures (above 6.38 MPa).