Production of trioxane

Trioxane is produced by maintaining formaldehyde in concentrated aqueous solution with an acid catalyst at between 0 DEG and 200 DEG C. and distilling off the trioxane, the distilling being performed in the presence of methanol, ethanol and/or a hemiformal thereof in sufficient amount to prevent the deposition of formaldehyde polymers in the apparatus. The trioxane is recovered from the distillate e.g. by extraction with a water immiscible solvent, evaporation of the solvent and subsequent distillation of the residue. The residue may be treated with a base before or during the subsequent distillation. U.S.A. Specifications 2,347,447 and 2,465,489 are referred to.