Experiments and a generalized model of the chemical equilibrium of transacetalization and oligomerization of poly(oxymethylene) dialkyl ethers

•Complex multicomponent systems are analyzed by NMR spectroscopy.•An entirely predictive model to describe the chemical equilibrium is presented.•Oligomerization is independent of chain length and alkyl group.•Distribution of terminating alkyl groups follows simple statistics. Poly(oxymethylene) dialkyl ethers (OAE) are oxygenated oligomers that feature favorable physical properties like emission-reducing potential when used as fuels in combustion engines. This work presents a generalized model to describe the chemical equilibrium of water-free mixtures containing OAE, with various terminating alkyl groups and chain lengths, and 1,3,5-trioxane as anhydrous formaldehyde source. The entirely predictive model is based on a generalized equilibrium constant for the formaldehyde oligomerization and statistical considerations. Reaction experiments with various feed compositions are performed at different temperatures and samples are analyzed by NMR spectroscopy. OAE with chain lengths n⩽5 are quantified. The model performs very well when compared to the experimental results of the present work and is thus able to fully describe the chemical equilibrium in mixtures containing OAE and a formaldehyde source. The presented model serves as reliable base for further extensions regarding more complex alkyl groups and systems containing water and alcohols.