Poly(oxymethylene) dimethyl ethers (OMEs) are attractive components for tailoring diesel fuels. They belong to the group of oxygenates that reduce soot formation in the combustion when added to diesel fuels and can be produced on a large scale from methane-based products. This opens a new route for gas-to-liquid technology. The present work deals with a particularly favorable route for the large scale production in which OMEs are formed from methylal and trioxane. An OME process based on these educts is designed using two process models of varying depth. In a hierarchical optimization, in which the optimum obtained with a reduced model is used as a starting point for the optimization with the detailed model, an optimal design is found. The resulting design is further adopted to practical needs including a possibility of side-product purge. This work shows that OME production from methylal and trioxane is feasible with technology that could be used in very large scales. The physical property model that is required for the design of the OME process is described in the present work. It is based on literature data on thermo-physical properties and reaction data from previous work of our group. That database is complemented in the present work by measurements of the density of pure OMEs and the vapor-liquid equilibrium in the system (dioxymethylene dimethyl ether + trioxane). (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.