GB663672A - New or improved process for the recovery of polyglycerols from distillation residues - Google Patents

Abstract

Dioxane is employed as the solvent in a process for obtaining polyglycerols from glycerine pitch by solvent extraction. Glycerine pitch is the residue remaining from the distillation of crude glycerin and consists mainly of polyglycerols together with some glycerin and, in the case of glycerin obtained from soap lyes, common salt. It also contains other inorganic salts, soap and salts of organic acids other than soap acids. The polyglycerols, together with any glycerin that may be present are extracted from the glycerin pitch by treating it with dioxane, the dioxane solution is separated from undissolved materials and distilled. The extraction is preferably carried out with hot dioxane. The pitch may be treated with hot dioxane, the resulting solution separated and cooled in stages to affect fractional separation of the polyglycerols. If desired, two fractions may be obtained by cooling the hot solution and obtaining one by drying the product which separates out and the other by evaporating the dioxane from the remaining cooled solution. The pitch may be purified before extraction by any known method and in the case of pitch obtained from glycerin resulting from the manufacture of soap it is useful to remove the greater part of the salt present. Instead of treating the pitch itself a crude extract of polyglycerols therefrom, e.g. an extract obtained by using aliphatic alcohols having from 3 to 5 carbon atoms in the molecule, may be used. The extraction can be made by first distributing the pitch or crude polyglycerol over a large area of surface before extraction with dioxane. For example, hot glycerin pitch may be mixed with sawdust, alumina or silica gel before extraction. In the examples, glycerin pitch is extracted with dioxane at elevated temperature and the dioxane then distilled from the resulting solution.