Investigating the phase behavior of methane, ethane and their binary mixture confined in a 5 nm slit-like-pore with different wall types: Monte Carlo simulation study

This study investigates the phase behavior of methane, ethane, and their binary mixture in both bulk and 5 nm slit-like pores with silica, anhydrite, calcite, dolomite, and montmorillonite walls using grand canonical Monte Carlo simulation (GCMC). The results show that vapor densities increase and, liquid densities decrease with the reduction of the pore width for both pure components and binary mixtures. The critical pressure and temperature decrease significantly in confined systems compared to bulk systems, with the rate of decrease varying depending on the type of surface. The response of critical density to surface type is distinct, and the critical density can be higher or lower than that in bulk systems. Furthermore, the dew point pressure of the confined binary mixture between two surfaces of silica, anhydrite, calcite, dolomite, and montmorillonite is higher than its value in bulk systems, while the bubble point pressure in confined systems can be lower, equal, or more than its value in bulk systems, depending on the pore surface and temperature. • For pure components and binary mixture, the vapor densities increase and liquid densities decrease with the reduction of the pore width. • The critical pressure and critical temperature decrease in confined system in comparison with the bulk one, but the rate of decreasing varies depending on the type of surface. • The response of critical density to the type of surface was different and the critical density could be higher or lower than the critical density in the bulk system. • The dew point pressure of the confined binary mixture between two surfaces of silica, anhydrite, calcite, dolomite, and montmorillonite was higher than its value in the case of the bulk system. • The bubble point pressure in the confined system could be lower or more or even equal to what it is in the case of a bulk system This depends on the type of pore surface and temperature.