Mechanistic and Kinetic Insights into Nitrogen Chemistry: NH2‑Mediated H‑Abstraction and HCN Addition Pathways in NH3/Ethanol Combustion

To elucidate possible mechanisms of nitrogen chemistry between ammonia (NH3) and ethanol, the potential pathways of ethanol radicals (Wa, Wb, and Wc) following H-abstraction by NH2 radicals were primarily investigated including HCN addition, H-transfer, and dissociation reactions by quantum chemical calculations. The rate constants were solved in the master equation based on RRKM and TST theory and fitted to the Arrhenius equation. The results demonstrate that H-abstraction from C2H5OH by NH2 at the b-site is the most competitive, facilitating subsequent HCN addition. The HCN addition-entranced channel exhibits a negative temperature coefficient (NTC) behavior at 0.01 atm, and the onset of this effect is progressively delayed with pressure. The low-temperature reaction path of ethanol radicals with HCN is dominated by the initial adduct (WaHCN, WbHCN, and WcHCN) formation and subsequent isomerization. The multiple dissociation product channels become more competitive with temperature, especially the HCNH elimination. Findings from this study identify new growth pathways for NPAHs and OPAHs in the reaction of straight-chain molecules with HCN and provide comprehensive kinetic insights.