Continuous isolation of a high-melting material by distillation

In a continuous distillation process for the separation of a higher boiling material from a lower boiling material from an admixture thereof by

• vaporization and condensation utilizing a distillation apparatus,
• wherein the higher boiling material comprises a material which is solid at ambient temperature,
• wherein the lower boiling material comprises at least one material which has a lower melting point than the higher boiling material which is solid at ambient temperatures,
• wherein the distillation apparatus is a dividing wall distillation column or is a system of thermally coupled distillation columns, and
• wherein the distillation apparatus includes at least two offtake points, one for the higher boiling materials and above that, one for the lower boiling materials,
• the improvement wherein
• the admixture of higher boiling material and lower boiling material is fed into the distilling apparatus which is fitted with a condenser at the top of the distilling apparatus and above the offtake point for the higher boiling materials, a part of which condenser is in contact with the interior of the distilling apparatus, the temperature of that part of the condenser which is in contact with the interior of the distilling apparatus is controlled during distillation such that its temperature is lower than the melting point of the material which is solid at ambient temperature and the concentration of the lower boiling material in the upper portion of the distillation apparatus is kept sufficiently high such that there is substantially no deposition in the distillation apparatus of the said material which is solid at ambient temperature.