The molecular clusters in a supercritical fluid–solid system should be considered as a phase—thermodynamic principle and evidence

Abstract

In this work we propose a new thermodynamic principle in which a supercritical fluid (SCF)–solid system is divided into a solid phase, a cluster phase, and a bulk fluid phase, i.e., the molecular clusters in the system are considered as an individual phase. The phase equilibria of various SCF–solid systems are calculated using this principle in combination with Monte Carlo simulation and the Peng–Robinson equation of state (PR-EOS). It is shown that in the critical region of the supercritical (SC) solvents where the clustering is significant, the results calculated using this thermodynamic principle are much more consistent with the experimental data than those calculated using the conventional thermodynamic principle, confirming the validity of the principle proposed in this work.