Distillative freezing process for separating volatile mixtures and

Abstract

The distillative freezing process disclosed is useful in separating a mixture containing at least two volatile components, denoted respectively as A-component and B-component, by simultaneously vaporizing the two components from the mixture under a sufficiently reduced pressure to simultaneously crystallize B-component. The vapor mixture obtained is brought to a condensed state either by a simple condensation operation or a condensation-desublimation operation without being substantially pressurized. The process may be conducted to completely eliminate the liquid phase and bring the mixture into the two phase solid-vapor region. Then, the solid phase in no longer contaminated by the adhering liquid phase and gives a high purity B-component on melting. The process is particularly useful in separating mixtures containing close boiling components, such as styrene-ethyl benzene mixtures, p-xylene-m-xylene mixtures and ethylene-ethane mixtures. The process can therefore be used in producing high purity monomers for the plastic industries and high purity chemicals for other industries.