Crystallization of carboxylic acids e.g. adipic acid is carried out in an organic solvent such as an ether, alcohol, ketone, ester or nitrile in which the acid has limited solubility

摘要

(Re)crystallization of carboxylic acids is carried out in an organic solvent or a mixture comprising an organic solvent in which the acid has a solubility of = 15 wt.% at 20 deg.C. The solvent is an ether, alcohol, ketone, ester, nitrile, amide, sulfoxide, carbonate, halogenated organic solvent or organic solvent bearing a nitro or phosphorous group (or a mixture of these). The treatment of a reaction mixture resulting from the direct oxidation of a hydrocarbon into carboxylic acids in liquid solvent phase, using a catalyst, comprises: (a) decantation into two liquid phases (a higher non-polar and a lower polar phase) when the reaction medium allows it; and (b) distillation of the lower phase (or if necessary the whole reaction mixture) for separating the distillate and the distillate tail comprising the formed acid, the catalyst, heavy compounds, at least part of the solvent and optionally the intermediates and by-products of the reaction.