Solubility of the Single Gases Carbon Monoxide and Oxygen in the Ionic Liquid [hmim][Tf₂N]

Experimental data for the solubility of the two single gases carbon monoxide and oxygen in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) are reported for temperatures between (293.25 and 413.2) K. The maximum pressure (the maximum gas molality) was 9.8 MPa (0.27 mol·kg−1) for carbon monoxide and 9.1 MPa (0.31 mol·kg−1) for oxygen. The experiments were performed using a high-pressure view-cell technique operating on the synthetic method. Oxygen shows a slightly higher solubility than carbon monoxide under all conditions investigated, but the solubility generally remains very low. Both gases become less soluble in [hmim][Tf2N] with increasing temperature; however, the effect is not very pronounced and becomes ambiguous for carbon monoxide above 373 K. An extension of Henry’s law is employed in correlating the solubility pressures. The final results for the Henry’s constant (at zero pressure) of carbon monoxide and oxygen in [hmim][Tf2N] (on the molality scale) are represented within the experimental uncertainty (1 % for both gases) by ln(kH,CO(0)/MPa) = 5.3954 − 364.2/(T/K) − 0.002356 (T/K) and ln(kH,O2(0)/MPa) = 5.7618 − 505.1/(T/K) − 0.002802 (T/K), respectively.