Synthesis of poly(oxymethylene) dimethyl ethers from methylal and trioxane over acidic ion exchange resins: A kinetic study

Poly(oxymethylene) dimethyl ethers (POMDME) are fuel additives that can reduce the emissions associated with diesel fuels considerably. POMDME have been synthetized from methylal and trioxane, catalyzed by the acidic ion exchange resin Amberlyst 15. A batch autoclave reactor has been used to carry out experiments conducted up to equilibrium conditions. The resulting POMDME distribution is modelled using the Schulz-Flory distribution theory, which confirms a sequential chain growth with insertion of one formaldehyde molecule at each reaction step. The kinetic experiments were carried out in an isothermal continuous fixed-bed reactor. The influence of temperature (45–80 °C) and space-time (1.6–3.2 kg h/m3) on trioxane conversion and product selectivity was determined. A kinetic model of the reaction has been proposed and validated with the experimental results. It has been demonstrated that trioxane decomposition to formaldehyde is the kinetically limiting step of the reaction scheme, with an activation energy of 112.2 kJ/mol. POMDME chain propagation reactions are in equilibrium under the conditions studied.