Production of oxymethylene ethers (OME) as sustainable diesel fuel substitutes: continuous synthesis from dimethyl ether and trioxane and evaluation of catalyst stability

Oxymethylene ethers (OMEs) are currently being investigated as attractive substitutes for fossil diesel fuel. In particular, the properties of OMEs containing 3–5 formaldehyde units (CH$_3$O(CH$_2$O)$_n$CH$_3$ with n = 3–5) are similar and mostly compliant with current diesel specifications. With their production based on renewable methanol, OMEs can contribute significantly to a future sustainable mobility. This study elaborates an anhydrous, liquid phase OME synthesis based on dimethyl ether (DME). Using a newly designed continuous production plant, the performance of extruded zeolite catalysts based on a commercially available ZSM-5 material is evaluated. The characteristics of the produced catalysts are analyzed extensively and discussed. Comprehensive characterization of the spent catalyst as well as regeneration experiments were performed to investigate catalyst deactivation mechanisms. It was shown that deactivation mechanisms are similar to those observed in methanol-to-hydrocarbon processes. Thus, understanding of these aspects is improved and approaches for further optimization can be identified.