InterPore2026

Phase Behavior of CO2-Alkane Mixtures in Nanopores: Insights from Wang–Landau Transition-Matrix Monte Carlo Simulations

21 May 2026, 11:50

15m

Oral Presentation (MS13) Fluids in Nanoporous Media MS13

Speaker

Zhehui Jin (University of Alberta)

Description

The phase behavior of CO2-alkane mixtures plays a central role in fluid transport, storage, and displacement in nanoporous media, with direct relevance to geological carbon sequestration, enhanced oil recovery, gas separation, and CO2 utilization technologies. Under nanoconfinement, phase equilibria, stability limits, and adsorption behavior can deviate substantially from bulk behavior due to strong fluid-surface interactions and restricted pore geometry. Capturing these effects reliably remains a major challenge for both experiments and simulations.
In this contribution, we summarize a series of studies employing the Wang-Landau Transition-Matrix Monte Carlo (WL-TMMC) method to investigate CO2-alkane phase behavior in bulk and nanoporous systems. Compared to conventional Monte Carlo approaches, WL-TMMC provides direct access to free energy landscapes, enabling robust determination of vapor-liquid equilibria, van der Waals loops, and phase stability limits under confinement, quantities that are often difficult or inefficient to obtain using standard techniques. Benchmark comparisons demonstrate that WL-TMMC yields accurate and consistent phase behavior predictions for CO2-alkane mixtures across a wide range of conditions.
We apply this framework to CO2-hexane mixtures confined in nanopores representative of shale inorganic minerals (calcite, quartz, and muscovite mica) and organic matter (graphite), revealing how surface chemistry controls confined phase behavior and adsorption trends. Furthermore, by combining WL-TMMC with free-energy interpolation, we extend simulations of CO2-methane mixtures in metal-organic frameworks and quartz nanopores from a limited set of temperatures to a broad range (273-473 K), enabling efficient prediction of temperature-dependent phase behavior and adsorption without exhaustive simulations.
Overall, this contribution highlights the importance of phase behavior in nanoconfined fluids and demonstrates WL-TMMC as a powerful and versatile tool for studying complex CO2-alkane systems in nanoporous media, providing mechanistic insights and practical guidance for subsurface and energy-related applications.