Acid-Catalyzed Synthesis of Trioxane in Aprotic Media

The effects of solvent, acid specificity, acid concentration, added salt, and reaction temperature on the yields of trioxane and formic acid (byproduct) in paraformaldehyde + acid (or acid + salt) + aprotic solvent were investigated. The mechanism that underlies the yield of paraformaldehyde and the selectivity of trioxane was determined. A highly practical and efficient synthesis of trioxane by a salt-mediated and acid-catalyzed yield of paraformaldehyde in sulfolane media was developed. The method increased the yield of paraformaldehyde by more than 5 times and decreased the formic acid concentration by 10 times compared to the commercial synthesis of trioxane in an aqueous reaction system (formaldehyde + H2SO4 + H2O).