Development of a new industrial process for trioxane production

Abstract

This paper reports on the development of a new industrial process for the production of trioxane ( C 3 H 6 O 3 ) , the cyclic trimer of formaldehyde ( CH 2 O ) . Trioxane is synthesized from concentrated aqueous formaldehyde solutions, which are inherently reactive complex multicomponent mixtures. Based on the knowledge on the physical chemistry of these complex solutions, reliable modeling of processes containing formaldehyde solutions has recently become possible. This was the key to the process development of the present work. The new trioxane process uses solely distillations for the purification. This is a great advantage compared to the existing process in which an extraction step with tedious solvent recovery is necessary. Conceptual process design was carried out with ∞ / ∞ -analysis using reactive distillation line diagrams. They show the possibility of a pressure swing distillation. Distillation experiments were carried out to validate the results. They prove the feasibility of all distillation cuts and, hence, of the entire process. The resulting new process, including all recycles, was successfully simulated based on a rigorous physico-chemical equilibrium stage model using Chemasim. Moreover, quantitative 1H NMR experiments were carried out, in which the trioxane formation as well as the formation of important side products in highly concentrated formaldehyde solutions containing up to 0.10 g g - 1 sulfuric acid was studied at temperatures up to 338 K to gain reliable information on reaction kinetics, needed for process design.