Plural stage distillation of trioxane in the presence of a water-immiscible solvent

摘要

1,137,054. Production of pure trioxane. FARBENFABRIKEN BAYER, A.G. 13 Jan., 1966 [13 Jan., 1965], No. 1688/66. Heading C2C. Pure trioxane is obtained by distilling a mixture having a pH of from 1 to 3 of formaldehyde or paraformaldehyde, water, an acid and a trioxane organic solvent which is immiscible with water, separating out a solution of trioxane in the organic solvent from the vapours distilling over and, after the removal of the formic acid contained therein by means of an ion exchanger, separating the organic trioxane solution by fractional distillation into substantially pure trioxane and the organic solvent containing the impurities. The process is advantageously effected by distilling the initial mixture and introducing the vapours which distil over into the middle portion of a first distillation column, drawing off a substantially trioxane free aqueous formaldehyde solution from the sump of this column (which solution can be returned to the process after having been passed through an ion exchanger and optionally after having been concentrated), completely condensing in a reflux condenser the product forming at the head of the first distillation column, separating the organic and aqueous phases which are thereby formed, returning the aqueous phase to the head of the first distillation column, and feeding the organic phase containing the trioxane, after passing the organic phase through an ion exchanger into the middle portion of a second distillation column, such that the water-immiscible solvent, water and formaldehyde distil over at the head of said second column, while pure trioxane is obtained in the sump, the trioxane preferably being discharged in an inert gas atmosphere. Suitable solvents which are immiscible with water are, for example, methylene chloride, chloroform, benzene and cyclohexane. A suitable form of apparatus for carrying out the above process is described.