Reaction mechanism and light gas conversion in pyrolysis and oxidation of dimethyl ether (DME): A ReaxFF molecular dynamics study

To uncover the microscopic reaction mechanisms of dimethyl ether (DME) pyrolysis and oxidation, reactive molecular dynamics simulations were employed to investigate the reaction processes under various O₂/DME ratios and impurity environments at 2200 K–3200 K. The results show that DME pyrolysis begins with a decomposition reaction of CH₃OCH₃ → CH₃O + CH₃, ultimately leading to the formation of CO, H₂ and PAHs. The reaction pathways of DME oxidation contain light gas conversion and combustion. In fuel rich conditions, the oxidation produces mainly H₂ and CO, while in fuel lean conditions, the oxidation products tend to be H₂O and CO₂. The carbon components of DME are completely converted into CO₂ and CO regardless of O₂ content. In the presence of impurities H₂O or CO₂, the oxidation reaction pathway is altered, causing consumption and transformation of these impurities into active radicals such as OH, further promoting the progress of the reaction. The top three light gases produced are hydrogen, methanol and methane, and increasing H₂ production in the DME oxidation process can be achieved through both oxygen subtraction and water addition. The rate of formaldehyde generation during pyrolysis is higher than that during oxidation. However, a higher oxygen content leads to increased formaldehyde production.