Conceptual design of a novel process for the production of OME fuels

Poly(oxymethylene) dimethyl ethers (OME) are oxygenates of the general structure H₃C-O-(CH₂O)_n-CH₃ with n ≥ 2. OME are synthetic diesel fuels, which strongly reduce the soot formation and indirectly also the NOx formation in diesel engines. This work presents the conceptual design of a novel OME process, which employs aqueous solutions of formaldehyde and methanol as feedstock. Process-relevant data on physico-chemical properties are determined experimentally and models for their description are developed. This includes describing the chemical equilibrium and the vapor-liquid-liquid equilibrium in the system (formaldehyde + water + methanol + methylal + OME). The models are used for determining thermodynamic limits of the process like chemical equilibria and distillation boundaries. Based on that knowledge the novel OME process is designed. It consists of a reactor, two distillation columns, and a pervaporation unit. The first column is a reactive distillation in which OME with n ≥ 3 are separated from a complex reactive multicomponent mixture with more than 30 components. All critical units, including the reactive distillation and the pervaporation are tested in lab-scale experiments. The column profiles of the distillation experiments are well described by simulations using the equilibrium-stage model.