Revealing the aging mechanisms of solketal, oxymethylene ether, and mixtures thereof as promising e-fuels

Solketal and oxymethylene ether (OME) are two promising blending candidates for regenerative fuels (e-fuels), which could contribute to a holistic solution to the energy crisis. In this study the thermo-oxidative aging of these two e-fuels in their pure form as well as in binary mixtures with different ratios (3:1, 1:1, and 1:3) (vol%) is investigated. Herein, the reaction networks of the thermo-oxidative aging process of both e-fuels and mixtures thereof is elucidated based on intermediates and decomposition products determined via GC-MS. Furthermore, changes of important fuel-specific parameters like kinematic viscosity and density as well as total acid number during aging have been determined. The 3:1 solketal:OME (vol%) mixture exhibits a higher stability to thermo-oxidative aging than the pure fuel components or mixtures with other ratios. The viscosity value of this mixture is within the DIN EN 590 norm after accelerated aging of 72 h (viscosity (72 h) = 4.25 mm(2)/s)) unlike other blends. The maximum value of the total acid number of this aged mixture reaches only similar to 29 % of the maximum value of aged pure OME and has the lowest value of all mixtures. Furthermore, the formation of a precipitate could be successfully suppressed in the 3:1 solketal:OME (vol%) mixture different from other mixtures. With these findings, this study contributes to the design of new sustainable fuels for the transport sector.