Heterogeneous condensation mechanism of methane-hexane binary mixture

The condensation mechanism of alkanes is an essential foundation for improving the liquefaction effi-ciency of natural gas. However, a microscopic understanding of this mechanism is still lacking. This study analyzes the homogeneous and heterogeneous condensation characteristics of methane and explores the influence mechanisms of n-hexane molecules. The results reveal that higher initial pressures cause more intense nucleation stages with more latent heat released. Moreover, changes in the monomer temper-ature lag behind changes in cluster temperature, which is particularly pronounced in low supersatura-tion systems. Trace amounts of n-hexane can greatly improve the nucleation rate and liquefaction ratio of methane. The pre-condensed n-hexane clusters serve as a surface for heterogeneous methane nucle-ation, lowering the nucleation barrier significantly. As the number of n-hexane molecules increases, the nucleation promotion effect is further enhanced. With increased subcooling, the promotion effect lg (J/J0) drops from 17 to approximately 2. Furthermore, the heterogeneous condensation of n-hexane and methane mixture comprises three processes: n-hexane condensation with methane molecular adhesion, methane aggregation on n-hexane nuclei, and surface growth of methane clusters accompanied by n -hexane dissolution. Moreover, methane with lower surface tension always dominates in the cluster surface region. (c) 2022 Elsevier Ltd. All rights reserved.