Theoretical and Modeling Study about the Low-Temperature Reaction Mechanism Between Oxymethylene Ether-2 (OME₂) Radicals and O₂

Abstract

Oxymethylene ether-2 (CH3–O–CH2–O–CH2–O–CH3, OME2), a carbon-neutral fuel, was hydrogenated from CO2 captured in air or exhaust gases and reused for synthesis with renewable electricity. In the current work, two different potential energy surfaces (PESs) for the reaction of OME2 radicals with O2 were constructed at the CCSD(T)/CBS//M062X/6-311++G(d,p) level. Based on the Rice–Ramsperger–Kassel–Marcus (RRKM) theory and transition state theory, the temperature- and pressure-dependent rate constants for the relevant reactions on the PES were calculated by solving the master equation. The Arrhenius equation has been used to fit the temperature- and pressure-dependent reaction rate constants. The main reaction channels on the PES are discussed, showing that initial adduct generation and intramolecular H-transfer reactions are the key reaction channels for low-temperature combustion. Among them, the HO2 concerted elimination reaction channel needs to overcome higher energy barriers leading to uncompetitive HO2 concerted elimination reactions. The calculated rate constants were updated to the OME2 combustion model, and the updated model is in considerable agreement with experimentally measured data on the ignition delay time in the shock tube. The present work provides support for further studies on the oxidation reaction of long-chain OME..