GB816208A - Trimethylolpropane - Google Patents

Abstract

Trimethylolpropane is separated from an aqueous solution containing trimethylolpropane and sodium formate by a process comprising treating the solution with a liquid solvent for trimethylolpropane so as to obtain an aqueous phase containing sodium formate in solution and a solvent phase comprising a solution of trimethylolpropane in the liquid solvent, the solvent being one which dissolves little water and is of low solubility in the aquous phase, separating the phases and recovering trimethylolpropane from the solvent phase. The preferred solvent is ethyl acetate but other solvents, e.g. esters of alcohols containing 2-4 carbon atoms with saturated monocarboxylic acids containing 1 to 3 carbon atoms, and n-butyl and amyl alcohols may be used. To recover the trimethylol-propane from the ethyl acetate or other solvent, the extract may be distilled to evaporate the solvent and any water present. The residue from this distillation may be further purified by distillation at sub-atmospheric pressure. Alternatively the extract may be distilled to remove the water and the residue treated, as by cooling, to cause crystallization of the trimethylolpropane. The production of the aqueous solution containing trimethylolpropane and sodium formate may be carried out by reacting butyraldehyde, formaldehyde and sodium hydroxide in an aqueous medium. In one method of carrying out the invention the extraction is carried out in a packed tower substantially filled with liquid. Ethyl acetate is introduced near the bottom of the tower and the aqueous solution to be treated is fed into the tower at a point above that of introduction of the ethyl acetate. The ethyl acetate which contains the trimethylolpropane and a minor amount of water is withdrawn from the top of the tower. The extraction proceeds most efficiently at a temperature of from 40 DEG to 70 DEG C. In the example, ethyl acetate is used as the solvent; the extract comprising water, ethyl acetate, trimethylolpropane and a small amount of sodium formate is steam distilled to remove practically all of the ethyl acetate and the residue is distilled at subatmospheric pressure to give pure trimethylolpropane as the distillate. Specification 816,210 is referred to.