Experimental study on the criticality of a methane/ethane mixture confined in nanoporous media.

For the first time, the critical region of a methane/ethane mixture confined in nanoporous media (SBA-15) is experimentally investigated using differential scanning calorimetry with an isochoric cooling procedure. The results reveal that the supercritical region of the confined fluid mixture exists at a lower pressure than its counterpart in the bulk space. The shift of the critical region is dependent on the pore size, which is similar to that of pure fluids [Tan et al., J. Phys. Chem. C, 2019, 123, 9824-9830]. Specifically, compared to that in bulk, the shift is greater for smaller pore size. The heat of capillary condensation of this mixture is also discussed. The findings in this work would shed some light on the understanding of confined phase behavior, especially criticality, in investigations toward more complex confined mixtures encountered in practical engineering application, for example, oil and gas recovery from unconventional reservoirs.