Clathrate phase equilibria for the water–phenol–carbon dioxide system

Abstract

AbstractClathrate phase equilibria for the ternary water–phenol–carbon dioxide system containing one‐guest and two‐host components were studied. Three four‐phase equilibrium loci for this ternary system were determined over wide temperature and pressure ranges. A quintuple point, thermodynamically unique, and invariant condition appeared in this type of ternary system, was carefully measured, and were 293.7 K and 57.2 bar. At this quintuple point, five individual phases of water‐rich liquid, phenol‐rich liquid, carbon dioxide‐rich liquid, phenol clathrate, and vapor could coexist in equilibrium. A new experimental technique was used to determine the liquid‐phase compositions coexisting with phenol clathrates at the isobaric conditions of 30.0 bar and six temperatures ranging from 278.2 and 303.2 K. A potential applicability of the clathration process to phenol separation from aqueous solutions was demonsrated in terms of phenol concentrations based on carbon dioxide‐free concentration. In particular, phenol separation by using high‐pressure carbon dioxide as a clarthrate‐inducing agent could be applied even to multiphase aqueous solutions over an entire range of phenol concentrations.