Advances in critical temperature shift modeling of confined pure fluids using the Kihara potential function

Abstract A multitude of research works have been conducted in the past decade to better predict the change of critical properties of fluids confined in nanopores, known as critical shift, due to its great impact upon calculations of fluid properties in tight reservoirs. Modeling of this phenomenon commenced with developing equations of state (EOS) and has been continuing with correlations, all based on the two-parameter Lennard–Jones (L–J) potential function. Although these approaches have tried to present passable estimations of critical shift, sufficiently accurate predictions of critical shift are still missing in the literature. In this study, the three-parameter Kihara potential, as a more physically realistic alternative, is used to develop the van der Waal (vdW) EOS, and accordingly, a fluid-dependent expression is derived to calculate the critical temperature of confined fluids, i.e., pore critical temperature ( $${T}_{\mathrm{cp}}$$ T cp ). Using 50 data points of $${T}_{cp}$$ T cp reports for normal alkanes in the literature, the average error of our model is only 2.23%, 6.4% less than that of the L–J model. Furthermore, despite simple correlations of previous works, herein the Kihara parameters are exclusively tuned for each component based on their $${T}_{cp}$$ T cp reports, which resulted in an average error of 0.4% for normal alkanes. Finally, the pressure–volume diagrams of vdW and Peng–Robinson EOSs associated with the Kihara potential function are comprehensively discussed. The findings of this study can help researchers with more accurate predictions of the critical temperature of fluids confined in tight porous media, thereby providing more precise calculations of fluid properties and behavior at equilibrium conditions.