Role of excess molar enthalpies in supercritical antisolvent micronizations using dimethylsulfoxide as the polar solvent

Abstract

The role of excess molar enthalpies ( H m E ) in the supercritical antisolvent (SAS) micronizations using dimethylsulfoxide (DMSO) as the polar solvent was investigated. Excess molar enthalpies for CO 2 + DMSO mixtures were measured using an isothermal high-pressure flow calorimeter under conditions of temperature and pressure typically used in SAS micronizations. In most cases, mixtures showed very exothermic mixing. A local temperature increase can be expected in the precipitation chamber as a consequence of the heat evolved when CO 2 dissolves in DMSO. Based on the H m E measurements, local temperature increases were calculated and shown to explain immiscibility of CO 2 and DMSO and agglomerated or irregular particles for average temperature and pressure conditions where complete miscibility and uniform particles could have been expected. H m E data were also discussed in terms of molecular interactions, phase equilibria, density and critical parameters previously reported for CO 2 + DMSO.