Effect of the phase behaviour of the solvent–antisolvent systems on the gas–antisolvent-crystallisation of paracetamol

The influence of the phase behaviour of the solvent–antisolvent system on the process conditions for the gas–antisolvent process is investigated. The two fluids are modelled by the Peng–Robinson equation of state while the dissolved solid is described by a Clapeyron-type approach. Based on the correlation of the ternary system, a liquid–liquid immiscibility region has been found which hinders the proper crystallisation of the solute. A thorough investigation of the binary solvent–antisolvent system by the global phase diagram methods yields a criterion for the proper choice of the solvent. The crucial property turns out to be the distance of the solvent–antisolvent system from the tricritical curve in the global phase diagram.