Theoretical Kinetic Study of NH2 Reactions With Dimethyl Ether and Diethyl Ether: Implications for Kinetic Modeling

Ammonia (NH₃) and hydrogen (H₂) have emerged as promising carbon-free fuels to help mitigate global warming by reducing greenhouse gas emissions. Our ongoing research currently focuses on understanding the combustion characteristics of NH₃ blends with oxygenates and hydrocarbons, uncovering the critical role of carbon–nitrogen cross-reactions in accurately modeling their combustion behavior. Amino (NH₂) radicals, which are abundant in ammonia and nitrogen-rich environments, strongly influence the low-temperature reactivity of NH₃-hydrocarbon/oxygenate mixtures, affecting overall reactivity and emission characteristics. Recognizing the importance of NH₂ radicals, we investigated the reaction kinetics of NH₂ with dimethyl ether (DME, CH₃OCH₃) and diethyl ether (DEE, CH₃CH₂OCH₂CH₃) using appropriate high-level ab initio and statistical rate theory methods. We computed the potential energy profiles at the CCSD(T)/cc-pV(T, Q)Z//M06-2X/aug-cc-pVTZ level of theory, analyzing the reactivity of NH₂ radicals at various C─H sites of these diethers. Incorporating these newly derived rate parameters, our updated kinetic model successfully captures previous experimental data, addressing the modeling challenges encountered in our earlier studies. Our findings, including insights into the impact of NH₂ radicals, contribute to an understanding of ammonia combustion and its potential in achieving carbon-neutral energy systems.