GB772574A - Separation of mixtures of pentaerythritol and dipentaerythritol - Google Patents

Abstract

Pentaerythritol is recovered from an aqueous solution containing pentaerythritol and dipentaerythritol by a process comprising taking the solution round a cycle which consists of evaporating water from the solution in an amount such that substantially only pentaerythritol crystallizes out, separating the resulting pentaerythritol crystals, so diluting and cooling the solution that substantially only dipentaerythritol crystallizes out, and separating the resulting dipentaerythritol crystals, the ratio of pentaerythritol to dipentaerythritol being at least 3:1 by weight at the commencement of the evaporation step. The crystals of pentaerythritol may be separated intermittently or continuously from the solution during the boiling operation. Sufficient water is added and the solution is cooled to such an extent that preferably the diluted and cooled solution is substantially saturated with both pentaerythritol and dipentaerythritol. Preferably the diluted solution is cooled to 60-70 DEG C. The solution left may be subjected to recycling, preferably with the addition of more feedstock. The mixture of pentaerythritol and dipentaerythritol used as starting material may be obtained by the reaction of formaldehyde and acetaldehyde in the presence of a basic catalyst.